Sexual differentiation and developmental stage identification of the Indian Cockroach, Pycnoscelus indicus (Blattodea: Blaberidae)

ABSTRACT

We found that sexual differentiation of all the nymphal stages of Pycnoscelus indicus (Fabricius) was possible by observing the developmental features of their posterior abdominal segments. Using this observation, the sex of even the 1st stage instar nymph could be determined. The female of the 1st to 6th stage instar nymph possess a V-shaped notch at the middle of the posterior edge of the 9th sternite. This notch is not seen in the male nymph. In the female 7th stage (final stage) instar nymph, the styli were not apparent and, the 8th and 9th sternites became degenerated and were covered over by the profoundly developed 7th sternite. In contrast, all stages of the male nymph showed the presence of styli. Thus, it is possible to differentiate the sex of all the stages, from 1st to 7th, of the nymph of P. indicus taxonomically. Moreover, it is also possible to identify the various specimens as to which stage the nymphal instar belong to, by counting the number of cercal segments from the ventral view.