Mating behaviour in Oncopeltus fasciatus (Dallas): effects of diet, photoperiod, juvenoids and precocene II

ABSTRACT. When adults of the large milkweed bug, Oncopeltus fasciatus (Dallas) were starved or fed non-host seeds, their mating activity during the 30 days following emergence was reduced by c. 50%. Topical applications of a juvenoid to adults fed non-host seeds usually increased mating activity, sometimes to near the level of milkweed-fed controls. An optimal juvenoid dose applied to adults reared and fed on sunflower seeds increased mating activity by only 9% to 28% from that of controls reared and fed on milkweed. Rearing and maintenance of the sexes on separate diets before pairing indicated that both the juvenoid-restored and non-restored milkweed stimulatory effects on mating probably acted exclusively on the males. Topical application of the anti-allatotropic agent precocene II to milkweed-fed males reduced mating activity by 75%. Simultaneous juvenoid treatment prevented most, but not all, of the precocene II effect. Juvenoid treatment completely prevented the depressed mating activity under short days. Rearing and maintenance of the sexes under different photo-periods before pairing under short days showed that photoperiod acted solely on the males. It is postulated that JH and one or more photosensitive and diet-sensitive factors in males regulate mating activity, JH being stimulatory but nonessential. A partial dietary control over mating may optimize male activity according to the population density and female reproductive activity.