Endocrine control of wing morph-related differences in mating success and accessory gland size in male firebugs

Abstract

Endocrine regulation has long been suspected to be a primary physiological cause of correlations between life history traits in insects. However, data showing hormonal control of wing morph-related differences in mating success of macropterous and brachypterous males are lacking. I investigated the relation between male mating success and the size of the accessory glands in the flightless firebug, Pyrrhocoris apterus (L.). Differential mating success of macropterous and brachypterous adult males depended on age. Brachypterous males had an early mating advantage (on days 3–14 after adult ecdysis), but macropterous males later gained this advantage (days 21–28 after ecdysis). The developmental patterns of mating success of the two wing morphs and the size of their accessory glands were positively related. The accessory glands were smaller and mating success lower in food-deprived brachypterous males than in normally feeding brachypterous males. Allatectomy of brachypterous males led to the accessory glands shrinking, whereas methoprene increased the size of the accessory glands of these males to that observed in same-aged controls. Mating success and the size of the accessory glands in macropterous males were also increased after methoprene treatment. This is the first report of endocrine control of a wing morph-related difference in mating success and its relation to the maturation rate of the accessory glands in wing-polymorphic insects.