Key to the adult females of Nesippus

1 4th thoracic segment with dorsal plates, genital complex without median sinus posteriorly.................... N. orientalis

- 4th thoracic segment without dorsal plates, genital complex with median sinus posteriorly............................. 2

2 Anterior region of genital complex broad (not neck-like), caudal rami broad armed with very small (almost invisible) setae................................................................................................. N. tigris

- Anterior region of genital complex narrow (neck-like), caudal rami not broad armed with clearly visible setae............ 3

3 Genital complex ovoid (slightly longer than wide) and about same width as cephalothorax, leg 4 exopod armed with 4 spines and 3 setae and endopod armed with 4 setae.......................................................... N. vespa

- Genital complex elliptical (longer than wide) about half width of cephalothorax, leg 4 exopod armed with 4 shortish spines…4

4 Genital complex with shallow and broad median sinus posteriorly, cephalon border with conspicuous papillae, specimens small.......................................................................................... N. nana

- Genital complex with deep median sinus posteriorly, cephalon border without conspicuous papillae, specimens larger.................................................................................................. N. crypturus