Chemosterilization of Oncopeltus fasciatus. 2. Effect of Tretamine and Metepa on Adult Males and Females1

Tretamine at 20 mg/kg caused a slight decrease in the longevity of unmated males and females Oncopeltus fasciatus (Dallas), but the delayed toxic effect was greater at 40 mg/kg and severe at 80 mg/kg (median lifespan decrease from 80 to 20 days). Mating activity and egg laying also shortened the lifespan; at 20 mg/kg tretamine might have prolonged life by causing a decline in the sexual activity, but at 40 mg/kg it shortened the lifespan of sexually active insects, At 20 mg/kg immature males were rendered sterile and immature females infecund for about 2 weeks, but then they partially recovered; at 40 mg/kg the sterilant effect was nearly total and permanent. Females mated with tretamine-sterilized males laid eggs that were mostly fertile but failed to hatch. Treatment of mature females did not interfere with maturation of large oocytes and laying of mature eggs, but maturation of new oocytes was either greatly delayed or permanently blocked. Metepa sterilized at dosages about 8 times greater than tretamine, and its action differed in some ways. There was little reduction in longevity even at dosages causing total and permanent sterility. However, eggs laid by females mated with treated males had an abnormally low percent fertilization, suggesting either a low level of sperm transfer or a high level of sperm inactivation.