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Revision of the Neotropical diving beetle genus Hydrodessus J. Balfour-Browne, 1953 (Coleoptera, Dytiscidae, Hydroporinae, Bidessini)

Abstract The Neotropical diving beetle genus Hydrodessus J. Balfour-Browne, 1953 (Coleoptera: Dytiscidae: Hydroporinae: Bidessini) is revised. Thirty species are recognized. The following new species are described: Hydrodessus bimaculatus sp. n. (Venezuela), Hydrodessus brevis sp. n. (Venezuela), Hydrodessus concolorans sp. n. (Venezuela), Hydrodessus continuus sp. n. (Venezuela), Hydrodessus disjunctus sp. n. (Suriname), Hydrodessus fasciatus sp. n. (Brazil), Hydrodessus imparilis sp. n. (Ecuador), Hydrodessus keithi sp. n. (Brazil, Colombia, Ecuador), Hydrodessus kurti sp. n. (Suriname), Hydrodessus kylei sp. n. (Suriname, Venezuela), Hydrodessus laetus sp. n. (Venezuela), Hydrodessus latotibialis sp. n. (Peru), Hydrodessus maculatus sp. n. (Guyana, Venezuela), Hydrodessus morsus sp. n. (Venezuela), Hydrodessus palus sp. n. (Venezuela), and Hydrodessus tenuatus sp. n. (Suriname). The following new synonyms are established: Hydrodessus fragrans Spangler, 1985 = Hydrodessus biguttatus (Guignot, 1957) syn. n. and Hydrodessus robinae Spangler, 1985 = Hydrodessus octospilus (Guignot, 1957), syn. n. One species is transferred from Hydrodessus to Amarodytes Régimbart, Amarodytes soekhnandanae (Makhan, 1994), comb. n. Habitus photographs (dorsal and lateral) and photos of the ventral surfaces are provided for most species. Line drawings of male and female genitalia and other diagnostic features are also provided along with distribution maps.


Introduction
Hydrodessus Balfour-Browne, 1953, was described to include a new species that Balfour-Browne (1953) thought might be an "…abnormal member of Bidessini…," but he was not certain. Young (1969) placed Hydrodessus in Bidessini, but it was later removed from that tribe (along with Amarodytes Régimbart) by Biström (1988) who placed it as incerta sedis with respect to tribe since members of the group lack bisegmented lateral lobes, the presence of which was then regarded as the only reliable synapomorphy of that tribe (Biström 1988). Amarodytes was later returned to Bidessini (Miller 2001) since at least some of its members have a spermathecal spine, bisegmented lateral lobes (in at least some species, see Benetti and Régil Cueto 2004), and crusher lobes of the proventriculus with five prominences, each of which characterizes members of Bidessini according to Miller et al. (2006). Hydrodessus was still, however, incerta sedis with respect to tribe (Nilsson 2001). A recent phylogenetic analysis by Miller and Bergsten (2014) resulted in Hydrodessus related to Peschetius and some Amarodytes, and this clade sister to the rest of Bidessini. The clade Peschetius + some Amarodytes + Hydrodessus does not have a known morphological synapomorphy, but this clade + other Bidessini (Bidessini in the broadest sense) has the distinctive synapomorphies of a spermathecal spine (absent or reduced in some Hydrodessus) and the crusher lobes of the proventriculus with five prominences (though not surveyed in all taxa, including most Hydrodessus, Miller et al. 2006). Based on this, Hydrodessus is recognized here as a genus of Bidessini following Miller et al. (2006). Given this history, it should be clear that much work remains needed to clarify relationships among these taxa. An important first step is to make better known the species in the group, which is the goal of this paper.
In general, members of this group are rarely collected with most specimens in collections found using lights at night. Only a few species have been collected in long series, though some of these series do include many species A few specimens have been collected from forest streams or stream margins, but little to nothing else is known of the biology of most Hydrodessus species. New species have been described regularly over several years (Balfour-Browne 1953;Guignot 1957;Spangler 1966;1985;Young 1970;Makahn 1994). Fortunately, these descriptions have largely been in the context of the group as a whole with keys and comparative diagnoses such that new species have largely been confidently identified as such. Discovery of a large number of new species, especially as the result of recent collecting in northern South America, and re-examination of the known species in light of the new discoveries have made clear, however, the need for a broad review of the genus. The goal of this project is to describe, key and illustrate all species in the genus, including 16 new ones.

Materials and methods
Dissections. Examination of male genitalia is critical for many Hydrodessus species determinations. Males were dissected by first relaxing the specimen in near boiling water. The genital capsule was then removed by inserting a pin with the apex bent into the side of the apex of the abdomen and hooking the base of the median lobe and pulling it out. The genitalia were then further disarticulated in a drop of glycerin on a microscope slide to isolate the median lobe and lateral lobes from other structures. All structures were then placed into a genitalia vial in glycerin and mounted on the pin with the specimen. Male genitalia were examined in glycerin.
Female genitalia were examined by first relaxing a specimen in near boiling water. A pin was then inserted into the end of the abdomen and moved along the suture between abdominal ventrites VI and VII and between tergites VII and VIII. The lateral junction of these sclerites was then cut with microscissors. Fine microforceps were then inserted into the abdomen and the female internal genital structures were grasped and the entire internal abdominal apex removed. These structures were then placed into a small glass tube with a 10% KOH solution. This tube was then placed in near boiling water to heat the KOH for about 10 minutes to macerate the soft tissues. The remaining structures were removed and placed in a weak acetic acid solution and then rinsed in much distilled water. Structures were stained using an aqueous solution of Chlorazol Black®. Structures were then placed into a genitalia vial in glycerin and mounted on the pin with the specimen. Female genitalia were examined in water. Examination in glycerin is not preferable since structures collapse, but in water they expand and are easily visible. Female genitalia are not described for all species here either because females are not available, the genitalia are damaged due to previous attempts to dissect the specimen, or female specimens are determined to be too rare or valuable to risk a dissection attempt which is often somewhat destructive to the specimen.
Measurements. Measurements were taken with an ocular scale on a Zeiss Discovery V8 dissecting microscope. Emphasis was placed on getting the diagnostic minimum and maximum measurements of structures rather than finding the average or taking a random sample. Measurements include: 1) total length (TL), 2) greatest width across elytra (GW), 3) greatest width of pronotum (PW), 4) greatest width of head (HW), and 5) distance between eyes (EW). The ratios TL/GW and HW/EW are also provided. extends anteriorly to meet the prosternal process, and the apex may be broad and meet the prosternal process broadly, or more narrowly rounded and only interfacing narrowly with the prosternal process. The surface of the process may be flat to distinctly longitudinally impressed. The lateral margins of the process are distinctive in all species, and in many species these margins extend posteriorly on the surface of the metaventrite as a pair of carinae. These carinae may be well developed and extend posteriorly to the posterior margin of the metaventrite at or near the anterior limit of the metacoxal lines. In some species the metaventrite carinae and the metacoxal lines form a continuous carina. In others, the metaventrite carina meets the posterior margin mediad of the metacoxal lines. The carinae may be straight or variously curved, they may be only slightly divergent posteriorly, or strongly so. In many taxa they do not extend across the entire metasternum, and in some they extend across the metaventrite only as lines of impunctate surface between the otherwise punctate regions of the sclerite.
Legs. The legs of Hydrodessus are relatively long. Variable features include the relative width of the pro-and mesotibiae and the shape of the metatrochanter and degree to which it is offset from the metafemur. The metacoxae vary in the degree of punctation on the surface and the relative width of the medial portion (distance between the metacoxal lines). The posteroapical surface of the metafemur is characterized by a series of spinous setae that are apically somewhat hooked, and increase in length apically.
Abdomen. The surface of the abdomen is somewhat variable in degree of punctation, and the apex of abdominal ventrite VI is somewhat variable in degree of curvature of the margin. It varies from rounded to relatively pointed.
Female genitalia. The internal female reproductive tract has an overall configuration typical of Hydroporinae (i.e. two genital openings with separate spermathecal and fertilization tracts). The length of the spermathecal and fertilization ducts varies between species and are quite long in many species. Species generally do not have a distinctive differentiation between the receptacle asp. n.rmatheca. Some species have a distinctive spermatheca spine, but others have a reduced spermatheca and do not have a spine.
Male genitalia. The male median and lateral lobes of the aedeagus are the most dispositive diagnostic structures in Hydrodessus. The lateral lobes are single-segmented and variable in shape, but are bilaterally symmetrical. The median lobe is variable in shape in both dorsal and ventral aspect. Most species have the median lobe bilaterally symmetrical, but a few species are distinctly asymmetrical.
Other sexually dimorphic features. Males have the pro-and mesotarsi somewhat more broadly expanded laterally with the ventral surface bearing several large adhesive setae. Females have the ventral surfaces with long, filamentous setae only. Some females of some species are more alutaceous on dorsal and ventral surfaces. Females of some species have the elytra distinctly expanded and lobate subapically with a corresponding impressed area on each side of abdominal ventrite VI or shorter and apically more rounded. Males of these species have the elytra evenly curved to a pointed apex and ventrite VI unmodified.

Diagnosis.
Hydrodessus are distinguishable from other Bidessini by the following combination: 1) the lateral lobes of the aedeagus comprised of a single segment (instead of two or three), 2) without basal pronotal striae, and 3) without prominent carinae on the disc of elytron and no large pores on dorsal and ventral surfaces. In addition, Hydrodessus do not have basal elytral striae, modifications to the anterior clypeal margin (except in one species), a transverse occipital line between the posterior margins of the eyes, nor a transverse carinae across the elytral epipleuron at the humeral angle.
Natural history. Relatively little is know of the natural history of most members of the group. A great many museum specimens were collected at lights. Other specimens were collected from forest streams, often in low numbers. Occasionally, longer series have been found in tropical forest streams. Larvae and other aspects of their natural history have not been described.
Taxonomic history. Hydrodessus has a complicated character combination, and because of this has had a history of ambiguous taxonomic placement. The genus was early placed in or near Bidessini, but not without reservation (Guignot 1957). Though Young (1967;1969) classified it in Bidessini, Biström (1988) restricted the definition of that tribe to those Hydroporinae with bi-or trisegmented lateral lobes, which are single-segmented in Hydrodessus (and at least some Amarodytes (Benetti and Régil Cueto 2004)). Hydrodessus was subsequently placed incerta sedis with respect to tribe until Miller and Bergsten (2014) placed it back into Bidessini. This was based on a large phylogenetic analysis including many DNA sequence data and morphology which resulted in Hydrodessus together with Peschetius (previously placed in Bidessini by Miller et al. (2006)) and some Amarodytes in a clade, and this sister to other Bidessini. Miller et al. (2006) expanded the definition of Bidessini to include taxa with 1) a spermathecal spine, and 2) five lobes on the crusher teeth of the proventriculus, which resulted in Peschetius and Amarodytes included in the tribe, but Hydrodessus was not examined comprehensively at that time. Based on evidence gathered for this revision, at least some Hydrodessus have a spermathecal spine, though not all do, and some have five-lobed crusher teeth on the proventriculus, though not all were examined. Based on this, and on evidence from Miller and Bergsten (2014), the genus is recognized here in Bidessini, and related to Peschetius and (at least) some Amarodytes.
The first species of Hydrodessus, H. siolii J. Balfour-Browne, was described along with the genus description (Balfour-Browne 1953). Subsequent to this, Guignot (1957) erected the new genus, Brinckius Guignot, with four new species. Spangler (1966) added two new species from Peru to Hydrodessus. In his treatment of the genera of New World Bidessini, Young (1967) was uncertain whether to synonymize Brinckius with Hydrodessus, though he keyed them out together. Nilsson (2001) regarded the synonymy of Brinckius with Hydrodessus to date to Young's (1967) paper. However, Young (1967, 83) seemed to make it clear at that time that he could not "… decide… whether Brinkius [sic] of Guignot should be accorded recognition." Even so, he soon (Young 1969) did synonymize Brinckius with Hydrodessus and provided a list of the included species. He then (Young 1970) added two more and provided a key to all the species. The next contribution was by Spangler (1985), who added five new species from Guyana and also provided a key to the species. Though not included in his concept of Bidessini, Biström (1988) listed the species. The last addition of species to the genus was three by , bringing the total to 17 valid Hydrodessus species prior to this revision.
Monophyly of Hydrodessus as deliminated here has not been demonstrated, and all the known diagnostic features described here for the genus are plesiomorphies. Other distinctive characters (potential synapomorphies) are variable within the genus. Many species have a lateral carina on the elytron extending posteriorly from the humeral angle, but not all do, and some of those that do have it only weakly developed. Most also have longitudinal carinae on the metaventrite approximately continuous with the metacoxal lines, but not all do. These two characters are also not always in the same combinations. All species have a similar overall appearance, robust, laterally discontinuous between the pronotum and elytron, elongate, with a variety of color patterns, and a somewhat characteristic shape for the prosternal and metasternal processes, but these are not particularly convincing as synapomorphies. Future research should concentrate on carefully examining the monophyly of the group and its relationships with Amarodytes and Peschetius, and possibly some Hypodessus Guignot, as well. It seems likely that Hydrodessus may eventually need division into multiple genera.
Distribution. Hydrodessus are characteristic mainly of northern South America from Ecuador and Peru to Brazil. The greatest known density of species is from southern Venezuela to Suriname. There are a few species extending south to Paraguay.

Key to the species of Hydrodessus
Two species, H. amazonensis and H. nanayensis, are problematic since no specimens were examined (the types were not found). Hydrodessus nanayensis is included in the key since, based on previous work, it appears to be very similar to (if not identical with) H. siolii. The other species, H. amazonensis, is not easily keyed with the characters included here since many of the states important for the key are not described for that species. It is included in the species treatments, however, and the male genitalia are relatively distinctive and diagnostic. Basal half of elytron approximately concolorous on disc, without distinct maculae (Fig. 27A), at most with diffuse, poorly-defined fasciae, though apical half of elytron often with maculae (as in Fig. 20A Prosternal process with lateral margins subparallel, slightly concave, posteriorly broadly rounded (Fig. 32C); female with apicolateral margin of elytron developed into flange (as in Fig. 5B (3) Prosternal process very broad (length/width < 1.8), lateral margins rounded, and broadly concave medially (as in Fig. 22C); carinae on metaventrite prominent, extending posteriorly to posterior margin (as in Fig. 22C) ......12 -Prosternal process narrower (length/wdith > 2), lateral margins variable, subparallel to sinuate, narrowly longitudinally concave medially (as in Fig. 33C); cariane on metaventrite indistinct, not generally extending to posterior margin except as narrow impunctate area (as in Fig. 33C Hydrodessus amazonensis Spangler, 1966: 380;Young 1969: 2;1970: 157;Spangler 1985: 89;Biström 1988: 37;Nilsson 2001: 236. Type locality. Peru, near Ituitos, from the Amazonas. Diagnosis. This species is difficult to diagnose from others since specimens were not available for examination, but based on the description and illustrations by Spangler (1966) the species is elongate with broadly curved lateral pronotal margins ( Fig.  2A), the elytra are patterned with testaceous and dark reddish-brown maculae (Fig.  2B), and the lateral elytral carina extend about 1/3 × length of elytron. The male genitalia in lateral aspect were illustrated by Spangler (1966). The median lobe is elongate triangular basally, relatively evenly curved medially with the apical portion straight and slender and the apex abruptly constricted and extremely slender and pointed (Fig.  2B). The lateral lobe is moderately narrow with the dorsal margin straight for most of its length and the apex rounded (Fig. 2C). The overall shape, color pattern and male genitalia should allow for specimens to be identified in the future.
Male genitalia. Median lobe in lateral aspect strongly curved medially, apical portion slightly curved, abruptly narrowed along dorsal margin subapically, apex narrowly pointed and slightly curved (Fig. 2B); lateral lobe in lateral aspect moderately broad in basal portion, apex slightly narrowed and straight to broadly rounded apex, with series of setae along medial surface apically (Fig. 2C).
Female genitalia. Females not described by Spangler (1966). Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae; female with sublateral carina absent basally.
Variation. According to Spangler (1966), specimens differ somewhat in size and coloration with some specimens having the dark coloration reduced or more enlarged. The presence of the sublateral carina is also variable, and it is absent in some specimens.
Distribution. This species is known only from the type locality near Iquitos, "from the Amazonas," Peru. (Fig. 44).
Habitat. Nothing is known of the natural history of this species. Discussion. The specimens on which this species (and H. nanayensis Spangler) were based were collected during the Catherwood Foundation expedition to Peru. The type material was not found in either the ANSP, where Spangler indicated the holotype was deposited (J. Weintraub, pers. comm.), the MZCZ (where many ANSP Coleoptera types were sent), or the USNM (where Spangler was working). Illustrations of the habitus and lateral aspect of the male genitalia are provided (redrawn in Fig. 2B,C), and the description of the species is extensive, though it excludes a number of important diagnostic features. The description presented here is based on Spangler's (1966) description and his figures and later keys (Spangler 1985;Young 1970). The extremely curved lateral margins of the pronotum, the distinctive color pattern on the elytron, and the shapes of the male genitalia are distinctive (Figs 2B, C), but H. amazonensis does not appear to correspond to any specimens examined during this study. Spangler (1966) indicates that the fine sublateral elytral carina is present in only two specimens he examined, the holotype and one other, suggesting that perhaps the series was mixed.
Specimens. No specimens were examined of this species, and the treatement here is based on the description by Spangler (1966). Young, 1970 Figs 8, 35, 46 Hydrodessus angularis Young, 1970: 155;Spangler 1985: 88;Biström 1988: 37;Nilsson 2001: 236. Type locality. Suriname, Carolina Creek, 10km S Zanderij. Diagnosis. This is a very distinctive species which is dorsally nearly concolorous red (Fig. 8A1,A2) except some specimens have the head and pronotum lighter orange and some specimens have poorly defined pale regions basally and subapically on the elytron. The lateral elytral carina is sharp and long, extending more than 3/4 length of the elytron (Fig. 8B). Specimens are robust with the lateral margins broadly rounded (Fig. 8A). Many specimens (not all) have the anterolateral angles of the pronotum conspicuously flattened and produced laterally into distinct, broad angle (Fig. 8A1). The anterior clypeal margin is beaded and somewhat projecting. The prosternal process is broadly quadrate and apically broadly trunctate (Fig. 8C). The metaventrite carinae are distinctive and posteriorly divergent (Fig. 8C). The male median lobe is basally triangular with the apical portion curved basally and apically approximately linear with the apex slight curved dorsad and narrowly rounded (Fig. 8D). The median lobe in ventral aspect is moderately broad with the lateral margins broadest submedially and evenly convergent to broadly pointed apex (Fig. 8E). The lateral lobe is very broad with the lateral margins approximately convergent to rounded apex (Fig. 8F).
Coloration (Fig. 8A). Head and pronotum yellow. Elytra brown to yellow or redbrown, with subapical, small, triangular macula and apex yellow in many specimens with other specimens evenly brown. Antennae and palps yellow to yellow brown. Legs yellow. Venter yellow to orange.
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect strongly curved medially, with base broad and subtriangular, apical portion more straight, with dorsal and ventral margins slightly expanded, narrowing to slender, narrowly rounded apex (Fig. 8D); in ventral aspect broad, lateral margins broadly curved, apically evenly convergent to pointed apex (Fig. 8E). Lateral lobe very broad basally, elongate, margins approximately evenly convergent to narrowly rounded apex which has small cluster of setae (Fig. 8F).
Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae.
Variation. The apical elytral maculae are indistinct in many specimens and are most conspicuous in teneral specimens. The most conspicuous variation is the degree of angulation of the lateral pronotal margins. Individuals from Suriname have the lateral pronotal margins strongly flattened and distinctly angulate (Fig. 8A1). Specimens from farther west, including Venezuela, have the lateral margins less strongly angulate (Fig. 8A2). The Suriname specimens also have the anterior margin of the clypeus more strongly concave that those specimens farther west. The specimens agree in other characters including the shape of the prosternal process, metasternum, and metacoxae and the shape of the male genitalia such that the variation in the lateral pronotal margin is here regarded as intraspecific variation.
Distribution. Hydrodessus angularis is known from Amazonas, Brazil through Guyana and Suriname to southern Venezuela (Fig. 46).
Habitat. Specimens have been collected from along a river margin, in a large sandy creek, a muddy oxbow pond, in detrital pools by a forest stream, and from lights at night. The species appears to be mainly associated with margins of forest rivers.
Discussion. Although the holotype of this species (in Rijksmuseum van Natuurlijke Historie, Leiden) was not examined, there is little doubt as to the identity of the species. That said, many specimens do not have the anterior angles of the pronotum nearly as angulate as others. In some of these specimens the anterior margin of the clypeus is not as strongly margined. The more angulate specimens are generally found in the eastern part of the range. The male genitalia are identical, and other features, such as the well-marked lateral elytral carina, the shape of the prosternal process, metaventrite carinae, and metacoxae are also the same. Even so, a greater sampling may eventually reveal that more than one species is actually involved.
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect broadly and evenly curved to narrow, narrowly rounded apex (Fig. 9D); in ventral aspect nearly parallel-sided throughout most of length, narrow, apically abruptly narrowed to narrowly rounded apex (Fig. 9E). Lateral lobe moderately broad basally, apically gradually narrowed, apex obliquely rounded with dense region of short setae (Fig. 9F).
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III slightly more broadly expanded than female and ventrally with several large adhesive setae. Some females specimens with fine dorsal microsculpturing which makes surface matte, other females and males dorsally shiny.
Variation. Specimens are conspicuously variable in size. There are relatively few specimens available to determine whether there is a geographic component to size variability, and other attributes (male genitalia, etc) do not evidently vary with size. There is some variation in the extent of elytral maculation. Given the variation, it is certainly possible that multiple species are involved, thought the diagnostic characters are consistent across the specimens examined.
Distribution. This species has been collected from Para, Brazil north through Suriname and Guyana to southern Venezuela (Fig. 49).

Habitat. Specimens have been collected from blacklights in tropical forests and from the margins of a river and a flooded forest stream.
Discussion. Although the holotype of H. biguttatus was not found, a paratype specimen was examined and compared with the holotype and other material of H. fragrans. The H. biguttatus paratype is a male, and is dissected, but the genitalia are not with the specimen. Nevertheless, the specimen agrees well with specimens of H. fragrans. In particular, these specimens all have the apices of the elytra distinctly dehiscent and the apex of the metatrochanter minutely but distinctly bispinous with a small spine at the dorsal apex and a slightly smaller spine at the ventral apex. Spangler (1985) diagnosed H. fragrans from H. biguttatus mainly on coloration and punctation, but these differences are well within the typical range of variation of species of Hydrodessus. For this reason, H. fragrans Spangler, 1985 is placed as a junior synonym of H. biguttatus (Guignot, 1957), syn. n.
This species, though widespread, is rarely collected and has not been collected in long series.
Specimens Diagnosis. This species is moderately elongate and dorsally and ventrally nearly concolorous red, except with small pale, subtriangular maculae subapically and the apex of the elytron is narrowly pale (Fig. 10A). The elytral apices are not dehiscent (Fig. 10A). The lateral elytral carinae extend about 1/4 length of the elytron (Fig.  10B). The prosternal process is very broad, broadly excavated medially, and slightly broader anteriorly (Fig. 10C). The metaventrite carinae are prominent, not medially constricted and posteriorly somewhat divergent, but the posterior apices are located distinctly mediad of the anterior apices of the metacoxal lines (Fig. 10C). The male median lobe in lateral aspect is relatively small basally with the apical portion slender, linear medially, abruptly curved subapically and with apex linear and narrowed to pointed apex (Fig. 10C). The median lobe in ventral aspect is bilaterally symmetrical and very broadly expanded medially (Fig. 10D). Apically the median lobe is abruptly broadly angulate (Fig. 10D). The lateral lobe is moderately broad, curved basally and apically broadly narrowed to narrowly rounded apex (Fig. 10F). This species is most similar to H. disjunctus and H. biguttatus. From H. biguttatus it differs in the absence of dehiscent elytral apices and the shape of the male genitalia. From H. disjunctus this species differs in size (H. bimaculatus are longer, TL > 3.5 mm) and the male genitalia are different.
Coloration (Fig. 10A). Head and pronotum red. Elytra red, with diffuse, yellow macula subapically and with apex yellow. Antennae and palpi yellow-red. Legs yellow. Venter red-brown, lighter on epipleuron and apex of abdomen.
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae.
Variation. Few specimens were examined and no significant variation was discovered.
Etymology. This species is named bimaculatus, Latin for "two spots," for the two maculae present apically on the elytra.
Distribution. This species is known only from Cerro de la Neblina, Amazonas, Venezuela (Fig. 44).
Habitat. Hydrodessus bimaculatus has been collected from "rocks in rapids" and "netted along margins" of the Rio Baria..

Hydrodessus brasiliensis (Guignot, 1957) Figs 11, 42
Brinckius brasiliensis Guignot, 1957: 40. Hydrodessus brasiliensis, Young 19691970: 158;Spangler 1985: 88;Biström 1988: 37;Nilsson 2001: 236. Type locality. Brazil, Pará State, Cachimbo. Diagnosis. Hydrodessus brasiliensis is characterized by being concolorous dark red-brown (Fig. 11A). The lateral elytral carina is prominent, extending to about 1/2 length of elytron (Fig. 11B). The pronotum is about the same width as the greatest distance across the elytra (Fig. 11A). Ventrally, the prosternal process is broad but has distinctive laterally-directed lobes anteriorly and is constricted medially (Fig. 11C). The metaventral platform is not strongly constricted and the metaventrite carinae are moderately divergent posteriorly with the posterior apices ending near the anterior apices of the metacoxal lines (Fig. 11C). The male median lobe in lateral aspect is broadly triangular basally with the apical portion broadly curved, slender and apically slightly sinuate, slender and sharply pointed (Fig. 11D). The median lobe in ventral aspect is bilaterally symmatrical and nearly parallel-sided with the apex broadly rounded (Fig.  11E). The lateral lobe is relatively narrow, medially curved and has the apical portion gently tapered to broadly rounded apex (Fig. 11F). There is a setal margin extending around much of the apical half (Fig. 11F). The species is not particularly similar to others in the genus.
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect with basal portion broad, medially broadly curved and slender, apically slender and narrowed to slightly but distinctly sinuate, sharply pointed apex (Fig. 11D); in ventral aspect moderately broad, lateral margins subparallel to rounded apex (Fig. 11E). Lateral lobe moderately broad basally, apically narrow with margins subparallel to narrowly rounded apex, apical margins with distinctive series of setae (Fig. 11F).
Female genitalia. Not examined. Sexual dimorphism. Only the male holotype was examined.
Variation. Only the male holotype was examined. Distribution. Hydrodessus brasiliensis is known only from Cochimbo, Para, central Brazil (Fig. 42).
Habitat. Nothing is known of the habitat of the species. Discussion. Only the male holotype specimen was examined of this species. Diagnosis. This species has the lateral elytral carina relatively short, present just at the humeral angle, and the body overall approximately concolorous dark red (Fig.  12A). Hydrodessus brevis is similar to H. palus in shape, and other structures, but that species is pale yellow, a bit smaller (TL = 2.0 mm) with H. brevis larger (TL = 2.5 mm). The male genitalia differ, as well, with the median lobe of H. brevis broader and apically not sinuate. Hydrodessus brevis is extremely similar to H. pereirai, but that species is considerably larger (TL = 3.9 mm). The male genitalia of H. pereirai are unknown so were not compared.
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III slightly more broadly expanded than female and ventrally with several large adhesive setae.
Variation. No significant variation was observed in the few specimens examined.
Etymology. This species is named brevis, Latin for "short," for the relatively short lateral elytral carina in specimens.
Habitat. The two specimens in the type series were collected from leaf pack from among rocks in a small rainforest stream.
Specimens Diagnosis. This species is dorsally shiny and concolorous dark red (Fig. 13A). The lateral elytral carina extends about 1/3 length of elytron (Fig. 13B), the prosternal process is very broad and excavated with the lateral margins rounded (Fig. 13C). The metaventrite carinae are not closely approximated anteriorly (Fig. 13C). Specimens are similar to H. continuus, but the metacoxal lines in H. concolorans meet the metaventrite/metacoxal suture at a prominent angle (Fig. 13C). The pronotum width is relatively narrowed compared with the greatest width across the elytra (Fig. 13A, EW/PW > 1.3). The male median lobe in lateral aspect is triangular basally, but very slender and evenly curved through apical portion (Fig. 13D). The apex is slender and pointed (Fig.  13D). The median lobe in ventral aspect is relatively parallel-sided to narrowed and narrowly rounded apex (Fig. 13E). The lateral lobe is basally moderately broad with apical half elongate triangular and the apex narrowly rounded (Fig. 13F).
Coloration (Fig. 13A). Head and pronotum red. Elytron red, apically red to redyellow; some specimens with pale subapical macula. Antennae and palps yellow-red. Legs yellow to yellow-red. Ventral surfaces yellow-red to yellow-brown, lighter on elytral epipleuron and abdominal apex.
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect evenly and moderately broadly curved throughout, basal portion small, apical portion long and slender to pointed apex (Fig. 13D); in ventral aspect narrow, lateral margins subparallel, apically evenly convergent to narrowly rounded apex (Fig. 13E). Lateral lobe elongate triangular, basally moderately broad, apically with lateral margins evenly convergent to pointed apex (Fig. 13F).
Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae.
Variation. Some specimens have pale subapical maculae on the elytra, especially teneral specimens, but most specimens do not have these maculae distinctly visible.
Etymology. This species is named concolorans, Latin for "concolorous," for the generally even coloration of specimens.
Distribution. This species is known only from the type locality area, Cerro de la Neblina, Amazonas, Venezuela (Fig. 42).
Habitat. Specimens have been collected from along the margins and from rocks in rapids in a forest river and from a muddy oxbow pond in a rainforest clearing.
Specimens Diagnosis. This species differs from others by being dorsally nearly concolorous but with indistinct paler regions subapically and apically (Fig. 14A), having the lateral elytral carina about 1/3 length of elytron (Fig. 14B), having the metaventrite platform (the area between the metaventrite carinae) not strongly constricted (Fig. 14C), and having the metacoxal lines approximately continuously curved with the suture between the metaventrite and metacoxae (Fig. 14C). Specimens are similar to H. concolorans and H. octospilus in general shape and coloration, but they have the metacoxal lines intersecting the metaventrite/metacoxal suture at an angle. The male median lobe is very broadly curved with an elongate triangular basal portion and the apical portion very slender, evenly curved, and apically sharply pointed (Fig. 14D). The median lobe in ventral aspect is broad with subparallel margins in the basal half (Fig. 14E). In the apical half it is strongly constricted to an elongate, slender apically narrowly rounded apex (Fig. 14E). The lateral lobe is very broad, evenly curved and tapered to the rounded apex (Fig. 14F). There is a dense series of setae in a cluster subapically on the dorsal margin (Fig. 14F).
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect strongly curved medially, apical portion more linear, basal region large, transverse, apical region slender, apically sharply pointed (Fig. 14D); in ventral aspect broad in basal half, lateral margins slightly concave, medially constricted and apical half strongly convergent to slender, apically pointed apex (Fig. 14E). Lateral lobe very broad basally, broadly curved to narrowly rounded apex, with dense brush of setae subapically along dorsal margin (Fig. 14F).
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae.
Variation. Few specimens were examined, and no significant variation was discovered.
Etymology. This species is named continuus, Latin for "continuous," for the metacoxal lines which are approximately continuously curved with the suture between the metaventrite and metacoxa.
Distribution. This species is known only from Cerro de la Neblina, Amazonas, Venezuela.
Habitat. One specimen was collected from the margin of a river and the other known specimens from a blacklight.
Specimens. The holotype male is in MIZA labeled, "VENEZUELA,T.F.Amaz. Diagnosis. This species is moderately elongate and dorsally and ventrally nearly concolorous red, without maculae on the elytra (Fig. 15A). The elytral apices are not dehiscent (Fig. 15A). The lateral elytral carinae extend about 1/4 length of elytron (Fig.  15B). The prosternal process is very broad and apically broadly truncate, broadly excavated medially, and slightly broader anteriorly (Fig. 15C). The metaventrite carinae are prominent, not medially constricted and posteriorly somewhat divergent, but the posterior apices are located distinctly mediad of the anterior apices of the metacoxal lines (Fig. 15C). The male median lobe in lateral aspect is relatively small basally with the apical portion slender, broadly and evenly curved (Fig. 15D). The apical portion is slightly constricted subapically, slender and pointed apically (Fig. 15D). The median lobe in ventral aspect is bilaterally symmetrical and slightly broadly expanded medially with the apical portion evenly convergent to moderately broadly pointed apex (Fig.  15E). The lateral lobe is moderately broad and with the lateral margins subparallel to the obliquely truncate apex which is somewhat, but distinctly, emarginate subapically (Fig. 15F). This species is most similar to H. bimaculatus and H. biguttatus. From H. biguttatus it differs in the absence of dehiscent elytral apices and the shape of the male genitalia. From H. bimaculatus this species differs in size (H. bimaculatus are longer, TL > 3.5 mm) and the male genitalia are different.
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae.
Variation. Only two specimens were examined, and no significant variation was discovered.
Etymology. This species is named disjunctus, Latin for "separated," for the distinctive distance separation between the posterior apices of the metaventrite carinae and the anterior apices of the metacoxal lines.
Distribution. This species is known only from the type specimens from the Tafelberg in Sipaliwini District, Suriname (Fig. 42).
Habitat. Specimens were collected from "forested creek margins." Specimens. The holotype male is in NZCS labeled, "SURINAME: Sipaliwini District N3°55.600', W56°11.300', 600m CSNR: Tafelberg  Diagnosis. This species is dorsally dark brown with distinctive, irregular fasciae on the elytra (Fig. 16A). The fasciate are somewhat linear-sided making the pale regions subrectangular (Fig. 16A). The lateral elytral carina is absent (Fig. 16B). The prosternal process is elongate and somewhat slender with the lateral margins subparallel (Fig.  16C). The anterior metaventrite process is moderately slender and medially impressed (Fig. 16C). The metaventrite carinae are distinct only anteriorly (Fig. 16C). The male median lobe in lateral aspect has a small basal region (Fig. 16D). The apical portion is evenly curved along the dorsal margin, but thickened subbasally and subapically along the ventral margin (Fig. 16D). The apex is elongate, slender and narrowly rounded api-cally (Fig. 16D). In ventral aspect the median lobe is slender, bilaterally asymmetrical and apically narrowly and obliquely rounded (Fig. 16E). The lateral lobe is moderately slender and broadly curved to a rounded apex (Fig. 16F). The species is perhaps most similar to H. siolii in body shape and structure, but that species has a different color pattern and the male genitalia are distinctive in each species.
Male genitalia. Median lobe bilaterally slightly asymmetrical, in lateral aspect broadly curved, distinctly expanded in two places along ventral margin, submedially and subapically, apex narrowed to pointed apex (Fig. 16D); in ventral aspect narrow, lateral margins unevenly convergent to asymmetrical apex which is slightly curved to right (Fig. 16E). Lateral lobe moderately broad basally, elongate slender apically to rounded apex, with series of setae along apical margin (Fig. 16F).
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III only slightly more broadly expanded than female and ventrally with several large adhesive setae.
Variation. Very little variation was examined in the few specimens examined.
Etymology. This species is named fasciatus, Latin for "striped," for the fasciate color pattern on the elytra.
Distribution. Hydrodessus fasciatus is known only from the type locality in Pará, Brazil (Fig. 45).
Habitat. Nothing is known of the natural history of this species. Diagnosis. This species is dorsally largely red with the pronotum orange and the elytral apex, lateral margins, and a moderately well-defined macula at about 2/3 length of elytron (Fig. 17A). The lateral margin is more broadly orange near the humeral angle (Fig. 17A). Also, there are very weakly-defined longitudinal fasciae indistinctly present on the anterior half of the elytron (Fig. 17A). The prosternal process has welldeveloped lateral lobes anteriorly (Fig. 16C). The metaventrite carinae are together strongly constricted immediately posterad to the metaventral process and are strongly divergent posteriorly (Fig. 16C). The male median lobe is elongate triangular basally with a sharp bend at base of apical portion (Fig. 16D). The apical portion is slender and weakly curved to near apex which is very slender and distinctly sinuate with the apex sharply pointed (Fig. 16D). The median lobe in ventral aspect is subparallel but bilaterally asymmetrical with the apex obliquely truncate (Fig. 16E). The lateral lobe is broadly triangular with the apex obliquely truncate (Fig. 16F). There are two series of setae, apically and along the dorsal margin (Fig. 16F).
Male genitalia. Median lobe bilaterally asymmetrical, in lateral aspect with basal region elongate subtriangular, abruptly curved medially, slightly curved in apical half, gradually expanded along ventral margin, apically sinuate with apex abruptly narrowed and apex pointed (Fig. 16D); in ventral narrow basally, lateral margins broadly curved, left margin more strongly curved, apex obliquely truncate (Fig. 16E). Lateral lobe broad, ventral margin broadly curved, dorsal margin slightly curved, apically narrowed with apex obliquely subtruncate, apex with series of setae and dorsal margin with medial series of setae (Fig. 16F).
Female genitalia. Not examined. Sexual dimorphism. Female not examined.
Variation. Only a single specimens of this species was examined. Etymology. This species is named imparilis, Latin for "unequal," for the the bilaterally asymmetrical male median lobe.
Distribution. This species is known only from the type locality in Provincia de Napo, Ecuador (Fig. 42).
Habitat. The single known specimen was collected at a black light. Diagnosis. Hydrodessus jethoeae is not particularly similar to any other species. Specimens are elongate and posteriorly attenuate (Fig. 18A). The dorsal surface is vaguely fasciate with variegations of yellow, brown and dark brown (Fig. 18A). The lateral elytral carina is elongate, extending about 1/2 length of the elytron (Fig. 18B). The prosternal process has distinctive lateral lobes anteriorly and is posteriorly abruptly narrowed (Fig. 18C). The metaventrite carinae are distinctive, extending across the metaventrite (Fig. 18C). They are slightly constricted anteriorly and moderately divergent posteriorly (Fig. 18C).
Coloration (Fig. 18A). Head and pronotum yellow-orange. Elytra orange with diffuse pale areas anterolaterally, mediolaterally, subapically and in broad V-shape at apex, also with diffuse, dark brown areas laterally and around subapical pale region. Antennae, palpi and legs yellow. Venter yellow, dark on some sutures, especially basal abdominal sutures.
Variation. Among the three specimens examined there is some minor variation in extent and pattern of coloration on the elytron.
Distribution. In addition to the type locality in Brokopondo District, Suriname, this species is known from two sites, one in Bolivar State, Venezuela and another in Sipaliwini District, Suriname (Fig. 42).
Habitat. Hydrodessus jethoeae has been collected from a river margin and at a UV light. Discussion. The type specimen had been dissected for examination in this study, and the base of the male median lobe and the lateral lobes were damaged and could not be illustrated. Other than the male type specimen, only two female specimens are known for this species, they are very similar to each other and distinct from all other species. They were also collected quite some distance from each other. Despite the lack of knowledge of males, it seems likely that future association of specimens with this species will not be problematic.
Specimens Diagnosis. Hydrodessus keithi has very characteristic coloration with the pronotum redi with testaceous margins and the elytra dark testaceous with distinctive maculae (Fig. 19A). There is a large subrectangular yellow macula at the humeral angle and a large subtriangular yellow macula at about 3/4 length of the elytron (Fig. 19A). The ventral surfaces are black. The lateral elytral carina is short and present only at the humeral angle (Fig. 19B). The prosternal process is relatively slender with moderately well-developed lateral lobes anteriorly (Fig. 19C). The metaventrite carinae are distinctive and strongly divergent posteriorly (Fig. 19C). The male median lobe in lateral aspect is slender and broadly curved with the apex subapically constricted on the ventral margin and apically sharply pointed (Fig. 19D). In ventral aspect, the apex is bilaterally symmetrical, broadly expanded and broadly rounded (Fig. 19E). The lateral lobe is large, broad and broadly sinuate with the apex broadly rounded (Fig. 19F). Males and females are dimorphic with the female apicolateral margin of the elytron distinctly flanged (Figs 5B, 19A1).
Coloration (Fig. 19A). Head yellow to yellow-brown, darker anterolateraly. Pronotum medially broadly yellow, laterally and posteriorly dark red. Elytron medially with broad, longitudinal black region subtending suture, medially with black or red-black region connecting to lateral margin of elytron, otherwise yellow, elytral coloration appearing as four, large, yellow maculae. Antennae and palpi yellow. Legs yellow except coxae, including metacoxae, black. Venter black except abdominal ventrites V and VI lighter, red-yellow and elytral epipleuron lighter yellowish apically.
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect broadly curved, with basal portion short and subtriangular, apical portion elongate slender and broadly curved, apically with ventral margin broadly sinuate, subapically expanded, and with apex slender and pointed (Fig. 19D); in ventral aspect slender, medially constricted, apically expanded and apex broadly rounded (Fig. 19E). Lateral lobe broadly sinuate, broad basally, apical portion more slender and evenly curved ventrad, apex narrowly rounded and with a small cluster of setae (Fig. 19F).
Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae; female with elytron prominently expanded and lobate subapically (Figs 5B,19A2), male evenly curved (Figs 5A, 19A1); male abdominal seternite VI evenly rounded across surface, apex with minute pointed lobe apically, female with prominent lateral depression on each side of VI.
Variation. Specimens are somewhat variable in coloration with some relatively lighter and others relatively darker.
Etymology. This species is named keithi in honor of the author's brother, Keith B. Miller.
Distribution. Hydrodessus keithi has been found in Ecuador, Colombia and central Brazil (Fig. 50).
Habitat. This species has been collected from blacklight traps. Nothing else is known about their habitat.
Specimens Diagnosis. This is a red species with the head and pronotum often somewhat lighter red and with moderately well-defined pale maculae on the elytra (Fig. 20A). There is one macula subapically that is triangular and a narrow macula at the apex (Fig. 20A). The carinae on the metaventrite are broadly divergent posteriorly with a prominent constriction immediately posterad of the metaventral process (Fig. 20C). This species is sexually dimorphic in body shape with the male apically broadly pointed (Fig. 20A1) and the female apically subtruncate to very broadly pointed (Fig. 20A2). The species is most similar to H. kylei which has a similar sexual dimorphism. That species has the eyes conspicuously emarginate (best seen in dorsal aspect). The male genitalia are different, as well. The median lobe in H. kurti is bilaterally symmetrical with the apex rounded in ventral aspect (Fig. 20E). In lateral aspect the median lobe is broadly curved with the apex very slender, sinuate and very sharply pointed (Fig.  20D). The median lobe in H. kylei is bilaterally asymmetrical with the apex obliquely truncate in ventral aspect. In lateral aspect the median lobe is similarly broadly curved but apically somewhat more robust (Fig. 21D). The lateral lobe is considerably narrower in H. kurti (Fig. 20F) than in H. kylie (Fig. 21F).
Coloration (Fig. 20A). Head red. Pronotum red to orange-red laterally, medially and along anterior margin with large, diffuse dark red area. Elytra red with subapical pale macula, apex pale (Fig. 20A). Antennae and palps yellow-orange to yellow. Legs yellow-orange to yellow, metacoxa dark red. Venter dark red on most surfaces, lighter orange on, prothorax, elytral epipleuron and apex of abdomen.
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae. Females with posterolateral margins of elytra expanded laterally and broadly lobate (Fig. 20A2), males with elytral margins not lobed (Fig. 20A1). Female abdominal ventrite VI not as laterally compressed as in male, and less strongly pointed medially.
Variation. Specimens vary somewhat in depth of coloration. In particular, the medial darkened region of the pronotum is variable with some specimens having that area smaller and others larger.
Etymology. This species is named kurti in honor of the author's brother, Kurt B.

Miller.
Distribution. Hydrodessus kurti is known only from the type locality in southern Suriname (Fig. 47).
Habitat. The type series was collected from a large, sandy creek. Diagnosis. Hydrodessus kylei is the only known Hydrodessus species with distinctly emarginate eyes (best seen in dorsal aspect) (Fig. 21A). This is a red species with the head and pronotum often somewhat lighter red and with moderately poorly-defined pale maculae on the elytra (Fig. 21A). There is one macula subapically that is triangular and a narrow lighter region apically (Fig. 21A). The carinae on the metaventrite are broadly divergent posteriorly with a prominent constriction immediately posterad of the metaventral process (Fig. 21C). This species is sexually dimorphic in body shape with the male apically broadly pointed (Fig. 21A1) and the female apically subtruncate to very broadly pointed (Fig. 21A2). The species is most similar to H. kurti which has a similar sexual dimorphism but does not have emarginate eyes. The male genitalia are also different. The median lobe in H. kurti is bilaterally symmetrical with the apex rounded in ventral aspect (Fig. 20E). In lateral aspect the median lobe is broadly curved with the apex very slender, sinuate and very sharply pointed (Fig. 20D). The median lobe in H. kylei is bilaterally asymmetrical with the apex obliquely truncate in ventral aspect (Fig. 21E). In lateral aspect the median lobe is similarly broadly curved but apically somewhat more robust (Fig. 21D). The lateral lobe is considerably broader in H. kylei (Fig. 21F) than in H. kurta (Fig. 20F).
Male genitalia. Median lobe bilaterally asymmetrical, in lateral aspect very strongly curved, with base extremely large and triangular, apical portion strongly curved, dorsal margin somewhat expanded, apex slightly sinuate and narrowly rounded (Fig. 21D); in ventral aspect broad basally, basal half with lateral margins subparallel, left margin straight to near apex, right margin strongly constricted submedially, margin divergent medially, apex broadly expanded and strongly obliquely truncate (Fig. 21E). Lateral lobe extremely broad, ventral margin very strongly curved, dorsal margin concave, apex a narrowly rounded lobe directed posteriorly (Fig. 21F).
Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae. The female elytral apex is more broadly rounded, and subapically slightly lobed on each side than in male.
Variation. The subapical and apical pale areas are variably distinctive between specimens.
Etymology. This species is named kylei in honor of the author's brother, Kyle B.

Miller.
Distribution. This species is found in Amazonas, Venezuela and in southern Suriname (Fig. 43).
Habitat. Specimens have been collected along the margins of a forest river, from a large, sandy creek, and at UV light.
Specimens Diagnosis. This species is robust and broadly rounded with a distinctive dorsal pattern of maculae and fasciae (Fig. 22A). The head and pronotum are yellow (Fig. 22A). The elytra are dark brown with yellow lateral margins and large, well-defined maculae subbasally, apically and at about 2/3 length of elytra (Fig. 22A). Specimens do not have a lateral elytral carina, the epipleural carina extends nearly straight from the humeral angle (Fig.  22B). The prosternal process is elongate oval with the apex broadly pointed (Fig. 22C). The metaventrite carinae are distinctive and moderately divergent posteriorly. The male median lobe is basally narrowly triangular (Fig. 22D). The apical portion is long and nearly evenly curved with the apex narrow (Fig. 22D). In ventral aspect the median lobe is bilaterally symmetrical with the lateral margins narrowed to narrowly rounded apex (Fig. 22E). The lateral lobe is elongate-triangular with a long series of setae along the dorsal margin (Fig. 22F). This species is similar to H. rattanae in coloration, overall shape, lack of lateral elytral carinae, shape of the prosternal process and metasternum and other features. The male genitalia are diagnostic (Figs. 22D-F). Hydrodessus rattanae is also more robust, not as attenuate posteriorly and the color pattern is a little different. The metacoxal lines and regions mediad to the metacoxae are different, too. In H. rattane the metacoxal lines are shorter, somewhat more divergent anteriorly and there are deep, longitudinal grooves along the medial margin of each metacoxal lines (Fig. 30C) that are missing in H. laetus (Fig. 22).
Coloration (Fig. 22A). Head and pronotum yellow. Elytra fasciate, brown to brown-red with large irregular yellow regions transversely near anterior margin and medially, apex yellow, macula distinctly delimited (Fig. 22A). Antennae, palps and legs yellow. Ventral sclerites yellow, black along some sutures including metacoxal / abdominal sclerite I, abdominal I / II and the anterior metasternal margin.
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect broadly and evenly curved, except apical 1/3 which is relatively straight, basal portion small and subtriangular, apical portion slender to narrowly rounded apex (Fig. 22D); in ventral aspect slender, lateral margins slightly curved, slightly narrowed medially and apex slender and narrowly rounded (Fig. 22E). Lateral lobe slender, elongate, without broad basal region, apex evenly narrowed to narrowly rounded apex (Fig. 22F).
Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae.
Variation. Specimens exhibit some minor variation in the extend of the maculae on the elytron.
Distribution. This species is known from Venezuela (Fig. 51).

Habitat. Specimens have been collected along a forest river and at lights.
Etymology. This species is named laetus, Latin for "colorful," for the attractive dorsal coloration of specimens. Discussion

Diagnosis. This species is part of a group including H. maculatus, H. phyllisae
and H. tenuatus that have the lateral elytral carina long (half or more the length of the elytron) (Fig. 23B), the prosternal process very broad (length/width < 2) (Fig.  23C), and the metaventral platform (the region between the metaventrite carinae) conspicuously constricted near the base of the metaventral process and fairly broadly divergent posteriorly (Fig. 23C). Hydrodessus latotibialis differs from H. maculatus in having the elytra red with only indistinct, weakly defined pale regions on the elytron (Fig. 23A) and from H. tenuatus in having the pro-and mesotarsi broad with a subapical emargination (Fig. 7B). From H. phyllisae, this species differs in size. Hydrodessus phyllisae are smaller (TL < 2.7 mm) than H. latotibialis (Tl > 2.9 mm). Also, specimens are more shiny than H. phyllisae which are dorsally more matte. Unfortunately, male specimens of H. latotibialis were not available, so the usually definitive male gentalia were not examined for comparison.
Male genitalia. Only females were examined. Female genitalia. Not examined. Sexual dimorphism. Only females were examined.

Variation. No signficant variation was detected.
Etymology. This species is named latotibialis from the Latin, lato, meaning "broad," and tibialis, meaning "tibia," for the relatively broad mesotibia in specimens.
Distribution. This species is known only from one locality in Tambopata Reserve, Peru (Fig. 42).
Habitat. The type specimens were collected from subtropical moist forest. Discussion. Two female specimens were examined of this species. Although ordinarily it is ill advised to describe new species of Dytiscidae based only on female specimens, this species appears sufficiently distinct that there should be little difficulty in associating specimens with this species in the future.
Specimens. The holotype and one paratype were examined. The holotype female is in USNM labeled, "PERU: Madre de Dios: Rio Tambopata  Diagnosis. This is a distinctive, elongate, dorsally maculate species (Fig. 24A). The dorsal base color is dark black with red areas medially and laterally on the pronotum and as moderately distinctive, irregular maculae subbasally, subapically and apically on the elytron (Fig. 24A). The lateral elytral carina is distinctive to about 1/2 length of elytron (Fig. 24B). The prosternal process is broad with subparallel lateral margins (Fig. 24C). The metaventrite carinae are prominent, constricted anteriorly and evenly divergent posteriorly (Fig. 24C). The male median lobe in lateral aspect is relatively narrow basally and abruptly curved at base of apical portion (Fig. 24D). The apical portion is relatively straight and medially distinctly expanded along ventral margin with the apex elongate, slender and sharply pointed (Fig. 24D). The median lobe in ventral aspect is slender to a distinct subapical lateral expansion with the apex convergent to a rounded apex (Fig. 24E). The lateral lobe is moderately slender and curved to rounded apex (Fig. 24F). The series of apical setae are on the ventral margin rather than the dorsal as in other species (Fig. 24F).
Coloration (Fig. 24A). Head reddish. Pronotum yellow, reddish medially and along posteromedial margin. Elytra red-brown with three yellow regions (Fig. 24A), one sub-basally with large, irregular macula extending from lateral margin to near suture, one irregular macula at about 2/3 length, and one at apex.
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect moderately curved, with basal portion subtriangular, apical portion curved medially, more straight near apex, subapically somewhat expanded along ventral margin, strongly tapered to elongate, pointed apex (Fig. 24D); in ventral aspect with lateral margins subparallel for most of length, subapically distinctly expanded laterally and apex broadly triangular (Fig. 24E). Lateral lobe moderately broad basally, evenly tapered and slightly curved to rounded apex which has series of marginal setae (Fig. 24F).
Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae.
Variation. Specimens vary in coloration with some specimens darker and others lighter.
Etymology. This species is named maculatus, Latin for "spotted," for the maculate coloration on the elytra in specimens.
Habitat. Specimens were collected "seined from rocks in rapids" and "netted along margins" of the Rio Baria. They have also been found in creeks and at a blacklight in a rainforest.
Specimens Diagnosis. This is the smallest Hydrodessus (TL < 1.5 mm). In addition, this species differs in having a low and rounded lateral elytral carina (Fig. 25B), a relatively narrow and apically pointed prosternal process (Fig. 25C), and the metaventrite carinae poorly developed (Fig. 25C). Specimens are concolorous yellow and parallel-sided (Fig. 25A). The male median lobe in lateral aspect is moderately broad basally, weakly curved and apically pointed (Fig. 25D). In ventral aspect the median lobe is slightly constricted subapically and apically rounded (Fig. 25E). The lateral lobe is broad basally and with margins apically evenly convergent to rounded apex (Fig. 25F).
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect broadly curved, with very broad basal portion, with medial expansion along ventral margin, apically with dorsal margin nearly stright, dorsal margin broadly curved to pointed apex (Fig.  25D); in ventral aspect broad, lateral margins slightly expanded medially, apically with margins slightly convergent to broadly rounded apex (Fig. 25E). Lateral lobe very broad basally, medially curved, apex broad with lateral margins straight and convergent to broadly rounded apex which has small cluster of marginal setae (Fig. 25F).
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae.
Variation. Very little variation was observed among the few specimens examined.
Etymology. This species is named morsus, Latin for "little bit," for the small size of specimens.
Distribution. This species is found only in Amazonas, Venezuela (Fig. 50).
Habitat. Nearly all the known specimens were collected at black light. Discussion. This extremely small Hydrodessus has only weakly developed lateral elytral carina and metaventrite carinae. The prosternal process is also relatively narrow. Together, these make this species only poorly placed in Hydrodessus, but the male lateral lobes have a single segment, and the overall body shape is consistent with the variation present in the genus. Even so, it is certainly possible this species does not belong in Hydrodessus.
the habitus was provided (Fig. 3). The description of the species is extensive, though it excludes certain important diagnostic features. The description presented here is based on Spangler's (1966) description and his figure as well as later keys (Spangler 1985;Young 1970). The shape of the beetle and the color pattern on the elytron are moderately distinctive (Fig. 3), and H. nanayensis does not appear to correspond to any specimens examined during this study. The apparent loss of the type specimen or the fact that it is a female may make determining to what species this name refers difficult. Young (1970) thought that H. nanayensis is likely conspecific with H. siolii, or, at most, a subspecies. The descriptions are very close and the shape and color pattern are very similar, but without examination of the type of H. nanayensis, this cannot be determined conclusively.
Specimens. No specimens were examined of this species, and the treatement here is based on the description by Spangler (1966).
Diagnosis. This is a relatively compact species with the dorsal coloration ranging from red to red-brown, sometimes with larger, indistinct pale areas or smaller, more distinctive pale regions (Fig. 26A). The lateral elytral carina is well-developed, extending beyond half the length of the elytron and with a distinct, impressed interruption at about half its length (Fig. 26B). The prosternal process is broad with the lateral margins subparallel and the apex broadly truncate (Fig. 26C). The metaventrite carinae are very well developed, not strongly constricted anteriorly, and evenly divergent posteriorly (Fig.  26C). The male median lobe in lateral aspect is triangular basally with the apical portion somewhat evenly curved with the apex subapically constricted and pointed (Fig. 26D). In ventral aspect the male median lobe is relatively broad with the lateral margins evenly convergent to a pointed apex (Fig. 26E). The lateral lobe is relatively narrow with the lateral margins straight and evenly convergent to the rounded apex (Fig. 26F).
Coloration (Fig. 26A). Head and pronotum orange-red. Elytron with base color red, with large, very diffuse pale areas anteriorly, subapically and at apex. Antennae and palps orange. Legs orange-red. Venter yellow-brown, red medially on surfaces, some areas nearly black including portions of prosternal and mesosternal processes and basal abdominal sutures.
Sculpture and structure. Head broad, anterior clypeal margin broadly curved; surface shiny with few, sparse minute punctures; eyes large. Pronotum subcordate, widest anterior of middle (Fig. 26A); lateral bead fine and continuous; surface shiny, covered with minute punctures, larger along anterior margin. Elytra moderately elongate, apically narrowly rounded (Fig. 26A); lateral carina distinctive and prominent, extending well beyond ½ length of elytron, slightly but distinctly impressed and interrupted near half its length; surface covered with minute punctures. Prosternum medially carinate and setose; prosternal process broad, with prominent anterolateral angles, lateral margins subparallel, apex broadly truncate, longitudinally strongly impressed (Fig. 26C). Metaventrite with anterior process moderately broad, laterally rounded, apex slightly truncated, medially flat; metasternal carinae flattened and broad, straight and divergent to posterior margin, terminating near anterior ends of metacoxal lines (Fig. 26C). Legs with most surfaces covered with fine punctures; metatibia with distinctive brush of dense, elongate setae on postero-apical surface; pro-and mesotibiae moderately broad; metatrochanter not strongly offset, apically pointed; metacoxa evenly covered with fine punctures; metacoxal lines broadly separated, somewhat sinuate and slightly divergent anteriorly (Fig. 26C). Abdomen shiny, evenly covered with fine punctures; apex of VI broadly pointed.
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect robust, moderately curved, basal portion broad, but not large, apical portion more straight, apex narrowed to slightly curved, nearly pointed apex (Fig. 26D); in ventral aspect broad, lateral margins broadly rounded, apex narrowed to narrowly rounded apex (Fig. 26E). Lateral lobe broad basally, apical portion elongate triangular, lateral margins straight and evenly convergent to rounded apex, with seta along apical margin (Fig. 26F).
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III slightly more broadly expanded than female and ventrally with several large adhesive setae. Female with abdominal ventrite VI slightly impressed on each side, apicomedially flattened and pointed; male with VI apically rounded, not impressed.
Variation. Specimens vary in extent of the dorsal maculae and intensity of dorsal coloration from nearly immaculate to distinctly maculate with larger pale regions.
Distribution. This species is known from Guayana and southern Venezuela to Brazil and south to Paraguay (Fig. 48).
Habitat. Hydrodessus octospilus has been collected from blacklights and forested creek and river margins.
Discussion. Examination of the male holotype specimens of H. octospilus and H. robinae indicates that these two names refer to the same species. Spangler (1985) erected H. robinae in part based on it having a longer lateral elytral carina compared with H. octospilus, but this is really not the case. The type specimen of a H. octospilus has the lateral carina extending distinctly beyond half the length of the elytron similar to the type of H. robinae. Also, the male genitalia of the two holotypes are extremely similar. Two female specimens from Paraguay (FSCA) are here assigned to this species. Diagnosis. This species has the lateral elytral carina relatively short, present just at the humeral angle (Fig. 27B), and the body overall nearly concolorous except somewhat darker on the apical half of the elytron (Fig. 27A). Hydrodessus palus is similar to H. brevis in shape, and other structures, but that species is dark red (Fig. 12A) and H. palus is pale yellow (Fig. 27A), and that species is a bit larger (TL = 2.5 mm) with H. palus smaller (TL = 2.0 mm). The male genitalia differ, as well, with the median lobe of H. palus more slender and apically sinuate (Fig. 27E).
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect somewhat curved, with basal portion narrowly triangular, apical portion very slender, broadly curved, apex slightly sinuate and narrowly pointed (Fig. 27D); in ventral aspect moderately slender, lateral margins broadly curved, constricted subapically with apex narrowly rounded (Fig. 27E). Lateral lobe moderately broad basally, long and elongate triangular with lateral margins evenly convergent to narrowly rounded apex which has a series of marginal setae (Fig. 27F).
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae.
Variation. Only two specimens were examined, and there is no significant variation between them.
Etymology. This species is named palus, Latin for "pale," for the overall yellow coloration of specimens.
Distribution. Hydrodessus palus is known only from the type locality in northwestern Amazonas, Venezuela (Fig. 42).
Coloration (Fig. 28A). Head yellow-brown. Pronotum yellow. Elytron yellow brown with vague pale macula subapically and apex yellow. Antennae, palps and legs yellow. Venter yellow to yellow-brown, darker brown on Metaventrite and other thoracic ventrites.
Male genitalia. Median lobe bilaterally symmetrical, in laterl aspect very broadly curved, broad basally, strongly constricted medially, more expanded, but slender in apical half, sinuate with apex slender and pointed (Fig. 28D); in ventral aspect nearly parallel-sided, moderately broad with apex broadly rounded (Fig. 28E). Lateral lobe very broad, terminating in small, slender, slightly curved lobe, with two patches of setae, apically on lobe, and subapically along ventral margin (Fig. 28F).
Female genitalia. Not examined. Sexual dimorphism. Only the male holotype examined.
Variation. Only the male holotype examined. Distribution. This species is known only from the Takutu Mountains of northern Guyana (Fig. 42).
Habitat. The single known specimen was collected from a blacklight in a forest clearing near some streams.
Specimens. The holotype male in USNM was examined, it is labeled, "GUYANA: Brinckius pereirai Guignot, 1957: 41. Hydrodessus pereirai, Young 19691970: 157;Spangler 1985: 88;Biström 1988: 37;Nilsson 2001: 236. Type locality. Brazil, Pará State, Cachimbo. Diagnosis. Specimens of this species are among the largest Hydrodessus (TL = 3.9). The lateral elytral carina is distinctly present only at the humeral angle, though it can be traced further along the elytron out to about 1/4 ts length (Fig. 4B), the dorsal and ventral coloration is approximately evenly dark red (Fig. 4A), the lateral pronotal margins are broadly curved (Fig. 4A), the prosternal process is broad with distinctive lateral lobes anteriorly (Fig. 4C), the metaventrite carinae are moderately distinctive, not strongly constricted, and moderately divergent posteriorly (Fig. 4C), the metacoxal lines are broadly separated and somewhat divergent anteriorly (Fig. 4C). Hydrodessus pereirai is superficially very similar to H. brevis in coloration, shape, and general structures, but that species has a maximum length of about 2.5mm. Unfortunately, males are not known for H. pereirai so the usually definitive character system of male genitalia is not available for comparison.
Coloration (Fig. 4A). Head, pronotum and elytra evenly dark red. Antennae and palps yellow-red. Legs yellow-brown to yellow-red. Venter dark red, yellow-red at apex of abdomen.
Female genitalia. Not examined. Sexual dimorphism. Only one, female specimen (the holotype) was examined.
Variation. Only one, female specimen (the holotype) was examined. Distribution. The species is known only from the type locality in Para, central Brazil (Fig. 45) (Fig. 29B), the prosternal process broad (length/width < 2) (Fig. 29C), and the metaventral platform (the region between the metaventrite carinae) conspicuously constricted near the base of the metaventral process and broadly divergent posteriorly (Fig.  29C). Hydrodessus phyllisae differs from H. maculatus in having the elytra red with only indistinct, weakly defined pale regions on the elytron (Fig. 29A) in having the pro-and mesotarsi broad with a subapical emargination (Fig. 7A). From H. latotibialis, this species differs in size. Hydrodessus phyllisae are smaller (TL < 2.7 mm) than H. latotibialis (Tl > 2.9 mm). Also, specimens are more matte than H. latotibialis which are dorsally shiny. Unfortunately, male specimens of H. latotibialis were not available, so the usually definitive male gentalia were not examined for comparison.
Sexual dimorphism. Male pro-and mesotarsi I-III slightly more broadly expanded than female and ventrally with several large adhesive setae; female specimens examined are dorsally more alutaceous.
Variation. Specimens vary somewhat in intensity of coloration.

Distribution.
Hydrodessus phyllisae is known only from the Takutu Mountains of Guyana and Cerro de la Neblina in southern Amazonas, Venezuela (Fig. 47).
Habitat. Specimens have been collected from blacklights and several forest habitats including muddy oxbow lakes, pools and leafpacks in whitewater streams, and stream margins.
Discussion. Two female specimens from Paraguari, Paraguay (FSCA) resemble H. phyllisae in many ways, but not such that they can be convincingly assigned to this species, and they are not included here as part of the concept of the species.
Diagnosis. Hydrodessus rattanae is robust and broadly rounded with a distinctive dorsal pattern of maculae and fasciae (Fig. 30A). The head and pronotum are yellow (Fig.  30A). The elytra are brown with yellow lateral margins and large, well-defined maculae subbasally, apically and at about 2/3 length of elytra (Fig. 30A). Specimens do not have a lateral elytral carina, the epipleural carina extends nearly straight from the humeral angle (Fig. 30B). The prosternal process is elongate oval with the apex broadly pointed (Fig.  30C). The metaventrite carinae are distinctive and moderately divergent posteriorly (Fig.  30C). The male median lobe is basally narrowly triangular (Fig. 30D). The apical portion is long and nearly evenly curved with the apex narrow (Fig. 30D). In ventral aspect the median lobe is bilaterally symmetrical with the lateral margins narrowed to narrowly rounded apex (Fig. 30E). The lateral lobe is elongate-triangular with a long series of setae along the dorsal margin (Fig. 30F). This species is similar to H. laetus in coloration, overall shape, lack of lateral elytral carinae, shape of the prosternal process and metasternum and other features. The male genitalia are diagnostic (Figs 30D-F). Hydrodessus rattanae is more robust, not as attenuate posteriorly and the color pattern is a little different (Fig.  30A). The metacoxal lines and regions mediad to the metacoxae are different, too (Fig.  30C). In H. rattane the metacoxal lines are shorter, somewhat more divergent anteriorly and there are deep, longitudinal grooves along the medial margin of each metacoxal lines (Fig. 30C) that are missing in H. laetus (Fig. 22C).
Coloration (Fig. 30A). Head and pronotum orange. Elytra fasciate, brown to brown-red with large irregular yellow regions transversely near anterior margin and medially, apex yellow, macula distinctly delimited, medial macula often separated into broad lateral marginal macula and smaller macula near suture (Fig. 30A). Antennae, palps and legs yellow. Ventral sclerites yellow, black along some sutures.
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae.
Variation. Specimens exhibit some minor variation in the extend of the maculae on the elytron.
Distribution. This species is known only from a couple localities in Suriname (Fig. 51).
Habitat. A series of specimens was collected along the margins of a forest creek.
Discussion. This species and H. laetus are similar to each other and very different from many other species of Hydrodessus in the shape of the lateral margins of the elytron. The epipleural carina (between the epipleuron and dorsal surface of the elytron) extends posteriorly directly from the humeral angle. There is no other lateral carina. It remains to be seen whether these species are together monophyletic with the other members of Hydrodessus.

Hydrodessus siolii J. Balfour-Browne, 1953 Figs 31, 43
Hydrodessus siolii J. Balfour-Browne, 1953: 56;Young 1967: 80;1969: 2;1970: 158;Spangler 1985: 88;Biström 1988: 37;Nilsson 2001: 236. Type locality. Brazil, Pará, Rio Cupari, Igarapé Ingatuba. Diagnosis. Hydrodessus siolii is a distinctive species with a pale head and pronotum and the elytra dark brown with the lateral margin yellow with distinctive, well defined yellow maculae (Fig. 31A). There is a prominent yellow macula on the elytral disc near the suture subbasally (Fig. 31A). There are a semiconnected pair of maculae at about 2/3 length of elytra (Fig. 31A). In some specimens the lateral macula is connected with the yellow lateral margin. Also, the elytral apex is yellow (Fig. 31A). The lateral elytral carina is absent (Fig. 31B). The prosternal process is elongate oval with the lateral margins slightly constricted medially (Fig. 31C). The prosternal process is elongate oval with the lateral margins somewhat constricted medially (Fig. 31C). The metaventrite carinae are indistinct and mainly marked by impunctate lines that are strongly divergent posteriorly (Fig. 31C). The male median lobe in lateral aspect is basally triangular (Fig. 31D). The apical portion is slender and evenly curved to a slender, narrowly rounded apex (Fig. 31D). In ventral aspect the median lobe is bilaterally symmetrical, apically convergent to elongate, slender, pointed apex (Fig. 31E). The lateral lobe is relatively slender, curved medially with the apical 1/3 relatively straight and slender to rounded apex (Fig. 31F). The species is perhaps most similar to H. fasciatus in body shape and structure, but that species has a different color pattern and the male genitalia are distinctive in each species.
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect gently curved, curvature more pronounced basally, basal region broad, apical portion slender throughout length, apex slender and pointed (Fig. 31D); in ventral aspect slender, lateral margins evenly convergent to middle, then slightly constricted and apically slender to pointed apex (Fig. 31E). Lateral lobe moderately broad basally, elongate slender apically, apex rounded, with series of setae along dorsal margin (Fig. 31F).
Female genitalia. Not examined. Sexual dimorphism. Male pro-and mesotarsi I-III slightly more broadly expanded than female and ventrally with several large adhesive setae. Females much more finely and densely punctate on all surfaces than males.
Variation. Specimens examined vary somewhat in the extend of maculation on the dorsal surface.
Distribution. This species is known from central Brazil and southern Venezuela (Fig. 43).
Habitat. This species was collected from "margem esquedra, entre detrito fibrosito" (Balfour-Browne 1953), or the "left bank, between fibrous detritous." Specimens have also been collected along a sandy forest stream in marginal leaf pack.
Discussion. The holotype (in BMNH) was not examined, but the male paratype (of one male and two female paratypes, Balfour-Browne 1953), which is now in the FSCA, was examined. Based on the description and the paratype examined, the identity of this species is clear.

Hydrodessus spanus
Diagnosis. This species has the elytron red with a moderately well-defined yellow macula at about 2/3 length of elytron (Fig. 32A). The pronotum is yellow and lighter in color than the elytron (Fig. 32A). The lateral carina on the elytron is low and rounded and mainly evident only near the humeral angle (Fig. 32B). The prosternal process is moderately narrow with the lateral carinae somewhat constricted medially and the apex rounded (Fig. 32C). The metaventrite carinae are only moderately distinct and clearly divergent posteriorly (Fig. 32C). The species is sexually dimorphic. Females have the anterolateral margin of the elytron flanged, unlike males. Females also have distinctive impressions on each side of abdominal ventrite VI. The male median lobe in lateral aspect is elongate triangular basally with the apical portion elongate, slender and curved with the apex distinctly sinuate and with a distinct angulation along the ventral margin subapically (Fig.  32D). In ventral aspect the apex is broadly rounded with distinct lateral teeth (Fig. 32E).
Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect strongly and broadly curved, with basal region short and robust, apical portion strongly constricted, apically subsinuate, subapically slightly expanded and apex pointed (Fig. 32D); in ventral aspect robust and broad, lateral margins slightly curved and slightly divergent to broadly rounded, abruptly expanded apex (Fig. 32E). Lateral lobe basally broad, apical portion elongate triangular, apex broadly sub-truncate, apicodorsal margin with series of setae (Fig. 32F).
Female genitalia. Not examined Sexual dimorphism. Male pro-and mesotarsi I-III more broadly expanded than female and ventrally with several large adhesive setae; female with elytron prominently expanded and lobate subapically, male evenly curved; male abdominal seternite VI evenly rounded across surface, apex with minute pointed lobe apically, female with prominent lateral depression on each side of VI.
Variation. Few specimens were examined, but they vary somewhat in the intensity of coloration.
Habitat. Specimens have been collected at a blacklight in a forest clearing near streams.
Coloration (Fig. 33A). Head and pronotum yellow. Elytra brown to yellow-brown with three regions of yellow: 1) one large basal irregular macula extending medially to near suture, covering anterolateral region except small, round, brown spot, 2) one moderately large, subapical macula, and 3) apex. Antennae, palps, legs and other ventral surfaces yellow.