Life in the dark: on the biology of the cavernicolous stonefly Protonemura gevi (Insecta, Plecoptera).

Protonemura gevi is a Palearctic stonefly with unique morphological adaptations for a cavernicolous life. In this study, the development, nymphal and adult feeding, adult behavior, and mate encounter mechanisms of this species are investigated. This species inhabits a stream flowing through a cave, in darkness and at a constant temperature. Nymphs of different sizes cohabit throughout the whole year, showing a nonseasonal life cycle. Nymphs at the entrance of the cave feed mainly on coarse particulate organic matter and hyphae, and nymphs at the end of the cave feed principally on detritus and occasionally on animal matter. Adults were present year-round and aggregated on emergent stones at the end of the cave. No drumming signals were recorded; therefore, this species seems to rely mainly on aggregation to maximize pair encounters. As shown in this study, P. gevi have adaptations suited to life in the dark and the completion of its entire life cycle inside a cave.