Changes in the probing responsiveness of starving tsetse flies (Glossina morsitans Westw.) (Diptera, Glossinidae)

Abstract Responsiveness to stimuli eliciting probing was measured in individual, suspended males of Glossina morsitans Westw. The standard stimulus was a warmed foam rubber ball offered from below; a positive response was recorded if the fly exsheathed its haustellum and probed the foam. During four days without food, probing responsiveness increased linearly from zero in mature flies, but with an initial step-up in tenerals. Each day's increase was steeper than the overall rate, and apparently modulated in the V-shaped pattern typical of other responses in tsetse flies. Starvation is thus seen to induce changes in feeding thresholds which parallel those induced in flight behaviour.