The beak may serve in a suctorial function. Its tadpoles apparently lack suctorial discs. The mouth is transverse, with a deep fold enclosing its corners and fleshy suctorial lips. The teeth are adapted for the suctorial feeding habits of the group. Instead, they have eight highly branched oral arms, along which there are suctorial minimouth orifices. Benthic marine enoplans are suctorial feeders and prey mainly on crustaceans. The lips are thick with pleats or fringes, though are not modified to be suctorial. The louse possesses a narrow suctorial mouthpart to feed on host haemolymph. Tadpoles have a suctorial disk, an adaptation to mountain streams. Male diving beetles have suctorial cups on their forelegs that they use to grasp females. Free-living marine suctorial nemerteans appear to be food specialists feeding primarily on amphipods. The mouthparts are rarely suctorial, though they are sometimes reduced; the maxillae always bear palps. These "suctorial organs" are the first of its two pairs of maxillae, modified in shape.