Caste developmental system of the Japanese damp-wood termite Hodotermopsisjaponica (Isoptera : Termopsidae)

Caste developmental pathways of the Japanese damp-wood termite Hodotermopsi s japonica Holmgren were estimated by measuring body parts. From the size d istribution of head-width, seven peaks were recognized in populations of la rvae. Of these peaks, the seventh has a wide range and variance, indicating that it represents several instars. The individuals that make up the seven th peak, which take the role of workers (pseudergate), are suggested to ent er the nymphal stage(s), which has brachypterous wing buds, prior to becomi ng alates. The pseudergates appear to be totipotent, that is, capable of di fferentiating into any caste, including reproductives and soldiers. Sixth i nstars and pseudergates have the potential to become soldiers via a presold ier stage. Although the evolution of caste systems in termites is controver sial, the linear developmental pathway found in this study is thought to be the typical pattern in lower termites. Sexual discrimination was also inve stigated, males and females being easily distinguished by examining the sev enth abdominal sternites of individuals older than fourth instar larvae. Bo th sexes appear to follow the same caste developmental pathway.