Aspects of the regulation of mating behaviour in tsetse

Abstract

The importance of maximum rates of insemination in female tsetse is emphasized in relation to their low rate of reproduction and to the possibility that density dependent regulation of tsetse populations may not be as rigorous as in many oviparous insects. Observations on the mating behaviour of tsetse are described and its regulation by sex pheromones which serve to identify females of the species is discussed. Laboratory and field experiments have shown that the sexual activity of G. m. morsitans males can be manipulated by presentation of synthetic sex pheromone on suitable decoys in the laboratory and in the field. Males that respond to decoys in the field are in the same nutritional state as others which are attracted to the models upon which the decoys are placed and are presumably seeking food. There is no reason to believe that sexual activity is restricted to a particular section of the population, and given a choice, it is proposed that mating is preferable to feeding in terms of gene survival for the individual male. The durations of copulatory responses are dose dependent and there is some evidence that they are inversely proportional to the frequency of encounters with decoys and hence to the density of flies. Techniques for the reduction of tsetse populations using sex pheromones in conjunction with suitable decoys and chemosterilants are being developed. The availability of pheromones in large quantities will permit their testing as sexual confusants among males and may lead to interspecific matings where more than one species occupies the same habitat.

Tsetse mating behaviour: effects of age and hunger in Glossina morsitans morsitans and G.pallidipes

“…However, Brady (1975) showed that changes in behaviour over the hunger cycle were most highly correlated with total body weight and abdominal weight, and these two in addition to duration of starvation, were more highly correlated to changes in behaviour than were per cent hydration, lipid content or residual blood meal. Re-analysis of Langley & Hall's (1984) data by the present author, shows that there were significant differences in dry weight (t=2.2, R 0 . 0 5 ) and dry weight plus fat FIG.…”

“…In contrast, the patterns of responsiveness of G.morsitans and G.pallidipes to mobile and stationary baits observed in the field by Vale (1974), supported Bursell's (1961Bursell's ( , 1966 general concept of fairly distinct, though overlapping, phases of mateorientated behaviour by replete flies and foodorientated behaviour by starved ones, provided the phase 3 component was modified to allow for a strong food-seeking response to mobile baits. Further opposing evidence, however, was presented by Langley & Hall (1984) who caught male G. m. morsitans landing on a black screen, or on pheromone-baited decoy-females mounted on the screen, in the field. They found no significant difference in the mean lipid or haematin contents of the two groups of flies, and concluded that it was invalid to distinguish a phase of mate-seeking behaviour exclusively for replete males.…”

Role of the male claw sensilla in perception of female mounting sex pheromone in Dermacentor variabilis, Dermacentor andersoni and Amblyomma americanum

“…Langley et al (1975) first described the cuticular contact sex pheromone of Glossina (morsitans) morsitans as 15, 19, 23-trimethyl-heptatriacontane; later, Carlson et al (1978) isolated, identified and synthesized the compound along with non-stimulatory components of the pheromone. Carlson et al (1978), Huyton et al (1980), Langley et al (1982) and Langley and Hall (1984) also noted that visual and tactile stimuli are important in the mating behavior of tsetse flies. Males do not contact non-moving females.…”

The orientation of males of Glossina morsitans morsitans Westwood (Diptera: Glossinidae) to pheromone-baited decoy ‘females’ in the field

“…One of these phases, 2, related to replete flies and proposed that they responded to and followed large moving objects without landing or feeding on them. Vale (1974) and Langley & Hall (1984) have shown that the nutritional states of flies caught on screen or decoys are not significantly different. However, while flies do mate at any stage in the hunger cycle, and therefore mating thresholds are not affected by hunger (Huyton et al, 1980), replete flies are less responsive to feeding stimuli than hungry ones, as their feeding thresholds are markedly affected by food-deprivation (Brady, 1973(Brady, , 1975.…”