Genetic variation of density responses in relation to wing polymorphism in the oriental chinch bug,Cavelerius saccharivorus Okajima (Heteroptera: Lygaeidae)

Responses to nymphal density in the determination of wing form were compared between the offspring from brachypter x brachypter crosses and those from macropter x macropter crosses of the oriental chinch bug, Cavelerius saccharivorus. In the offspring from crosses between macropters, there was a strong tendency for macropters to increase to a rather high level with increasing nymphal density in both sexes. In contrast to this, in the offspring from crosses between brachypters, the appearance rate of macropters attained a maximum value in moderately crowded conditions and conversely decreased to a lower level in more crowded conditions in both sexes. Thus density response patterns concerning the determination of wing form were quite different between the offspring from different crosses in the wing form, indicating that there is a genetic basis underlying wing polymorphism in this species. As for the body size of emerged adults, macropters tended to be larger than brachypters in the same crowded condition. Moreover, the rate of decrease of body size with nymphal density was lower in the offspring from crosses between macropters than in the offspring from crosses between brachypters. This indicated that the former offspring are more tolerant of nymphal crowding than the latter. The difference in such a tolerance against nymphal crowding between the offspring from different crosses was considered to be related to the difference in the appearance of macropters in the crowded conditions between them.