The Viability, Fertility and Behaviour of Tsetse Flies (Glossina morsitans) Sterilized by Irradiation Under Various Conditions

Abstract

Glossina morsitans pupae of known age were irradiated at different times during pupal life. The ages after which irradiation in air did not prevent development and normal eclosion, were identified. Irradiation at the earliest age which allowed normal eclosion of males resulted in decreased adult survival compared with pupae irradiated on the day of eclosion, but in both cases survival was improved by irradiating in an atmosphere of nitrogen. Pupae which had reached the day of peak male eclosion were stored at 10°—11° for 5 days and then produced a predictable flush of adult emergence following irradiation in nitrogen or in air. This technique, or the alternative of irradiation some days before eclosion is expected, would enable several days' collection of pupae to be treated as a single batch for the purposes of release in a sterile male control project. Laboratory measurements of several behavioural parameters showed that adult males, irradiated as pupae, can deviate from normal when compared with unirradiated controls. However, irradiation in nitrogen caused less alteration to behaviour than the lower doses in air required to achieve the same reduction in fertility. Measurements and estimates of the somatic and genetic effects of various irradiation treatments given under described conditions, were used to predict the treatment which would provide the optimal population suppression in a field control project involving the release of sterilized males. Computations have shown that the optimal sterilizing treatment may differ for different target levels of population reduction, and this concept may be of considerable significance in the control of oviparous insects with greater reproducti