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 at 28°C and dissected the resulting adults at various ages. While diapause characters could generally be distinguished at 3 d of age, the distinction between diapausing and reproductive bugs was not unambiguous because the morphological characters indicative of the respective conditions were not fully developed. Differences in the morphology of diapausing and reproductive bugs became more distinct with increasing age up to 10 d. In addition to the diapause characters previously reported (hypertrophied fat bodies and undeveloped ovaries) accessory gland condition in males was informative. Although we observed fat bodies characteristic of those previously reported (reproductive, translucent and sheet-like; diapause, white and in well-formed globules) appearance of the fat bodies was highly variable. Fat body condition alone was not an adequate criterion to distinguish diapausing bugs. These results provide baseline information to improve the accuracy of classification of physiological condition in future studies of L. hesperus diapause.