A megasporangium enclosed in a protective layer called an integument is known as an ovule. The appendages are attached to the soft ventral integument of the plate. Arthropods are covered with a tough, resilient integument or exoskeleton of chitin. The cuticle forms the major part of the integument of the Arthropoda. The nymph stages are black or very dark brown, with red integument between the sclerites. In herpetology, costal grooves refer to lateral indents along the integument of salamanders. These ovules are further protected by a double-walled integument. Since the avian integument is not equipped with sweat glands, cutaneous cooling is minimal. Both of these glands are part of the integument and thus considered cutaneous. With continuing maturation the cells enlarge in the outer integument. The seeds are usually flattened and/or winged, with a many-layered outer integument. The megasporangium bears an unopened distal extension protruding above the mutlilobed integument. The megasporangium bears an unopened distal extension protruding above the multilobed integument. Eventually, the fungus erupts from the integument of the larvae and forms a false skin. The integument evolved into complex, pennaceous feathers.