Effect of precocene II on the endocrine regulation of development and reproduction in the bug, Oncopeltus fasciatus

Large milkweed bugs, Oncopeltus fasciatus, were exposed to precocene II for different times as larvae or adults. Short-term contact during the stages in which the corpora allata are active (1 hr in the second instar, 12 hr in the young adults), inactivated the gland completely. Treatment during the last instar, in which the activity of corpus allatum is limited did not injure the gland which was subsequently activated in the young adults. The inactivation of the corpora allata resulted in precocious metamorphosis and degeneration of the prothoracic glands in younger larval instars and inhibition of vitellogenesis in adult females. However, the males with inactivated corpora allata were fertile. The corpora allata of treated insects remained inactive even when transplanted into an untreated insect. The effects of precocene II can be counteracted by subsequent application of juvenile hormone 1. The irreversibility of changes induced by precocene II holds promise for the practical application of compounds of this type as insect growth regulators if substances with a broad spectrum of activity and good persistency can be found.