Some effects of prolonged virginity on feeding and milk-gland activity in females of the tsetse Glossina austeni (Newst.)

The effects of virginity on feeding and milk-gland (MG) activity were investigated in 4-week-old virgin females of Glossina austeni. The flies take in smaller but constant amount of blood roughly equivalent to their own weight during each feed. This syndrome of feeding to a constant weight with time leads to fatbody hypertrophy largely because of decreased metabolic demands due to the absence of a larva. It is suggested that the small blood-meals of virgin females are probably related to the space limitations in their abdomens, and are probably hormone-mediated, possibly operating via the cuticle. The MG of virgin flies is well-differentiated but the cycles of synthetic activity which the distal MG tubules exhibit in mated flies during a pregnancy cycle are not so apparent in virgins. The secretions of this gland are used to nourish the developing larva and if the MG were very active the secretions produced would be lost. It is concluded that in virgin females the blood-meal is reduced in size, probably as a result, at least partly, of a reduction or absence of neurosecretory out-flow related to mating and ovulation, and the products of their blood-meal apparently are diverted not to the MG but to the fatbody for storage. These effects of virginity on blood-meal size, fatbody and MG activity can be reversed at any time by mating.