Observations of Diapause Characters in the Western Tarnished Plant Bug, Lygus hesperus

Knowledge of overwintering strategies of the western tarnished plant bug, Lygus hesperus (Knight) is essential to the development of ecologically-based management strategies. The adult diapause of L. hesperus has been studied, but temporal patterns in the development and exhibition of morphological characters of diapause have not been defined. We reared L. hesperus from egg to adulthood under long (14:10) and short (10:14, L:D h) photoperiods and dissected the resulting adults at various ages. While diapausing bugs could generally be distinguished from reproductive bugs at 3 d of age, the distinction was not unambiguous because the morphological characters of diapause were not fully developed. Differences in the morphology of diapausing and reproductive bugs were distinct at 7 and 14 d of age. In addition to the diapause characters previously reported (hypertrophied fat bodies and undeveloped ovaries) we found accessory gland condition in males to be a useful diagnostic character. Although we observed fat bodies characteristic of those previously reported (reproductive, translucent and sheet-like; diapause, white and in well-formed globules), we also observed a third fat body type composed of small, transparent glass-like spheres. This unique fat body type occurred in both reproductive and diapausing bugs, but was much more abundant in those that were diapausing. These results provide baseline information to improve the accuracy of classification of physiological condition in future studies of L. hesperus diapause.