chapter  23
8 Pages

Waterscorpions (Nepidae)

The family Nepidae is divided into two subfamilies, Nepinae and Ranatrinae, and five tribes: Nepini, Curictini, Goondnomdanepini, Austronepini, and Ranatrini (Lansbury 1974). Most of the family’s approximately 225 species are found in 2 of the 14 genera:

Laccotrephes

with ~60 species and

Ranatra

with ~110 species. Nepids derive their common name, waterscorpions, from their elongate, caudal respiratory

siphon. This movable siphon consists of two filaments, derived from the eighth abdominal tergum, which, when pressed together, form an air channel. Thrust through the water surface from below, the siphon conducts air to a subelytral air store via the insect’s tracheal system and spiracles on the dorsum of the first abdominal segment (Parsons 1972).