Active and resting behaviour of virgin and pregnant females ofGlossina morsitans morsitansWestwood (Diptera: Glossinidae) in the laboratory

Abstract

Activity in virgin and pregnant females of Glossina morsitans morsitans Westw. was very low and mostly took the form of short bursts of flight. Recently-fed virgins and females in early and mid-pregnancy were least active. In late pregnancy, activity increased and more walking occurred. In all classes of females, activity was least around midday, but the V-shaped curve became less pronounced as parturition approached. There was evidence of a slight preference for black over white surfaces when landing but a clear preference for black resting sites. Virgin females preferred to alight and rest on vertical surfaces at the borders of areas of visual contrast; pregnant females preferred to alight and rest on horizontal surfaces and showed no attraction to regions of contrast. In a horizontal light gradient, pregnant females selected lighter resting sites as the day progressed. In late pregnancy, there was an increasing tendency to rest in darker sites. Increasing the temperature in the light gradient caused an increase in activity around 34°C and a switch to photonegative behaviour. After larviposition, the females became strongly photopositive even at high temperature (38°C), but after a feed they reverted to the ' normal' photonegative response to high temperature.

Changing visual responsiveness in pregnant and larvipositing tsetse flies, Glossina morsitans

“…Finally, the lack of visual responsiveness before and around larviposition suggests that the contemporary inactivity (Brady & Gibson, 1983) and photonegativity (Rowcliffe & Finlayson, 1982) go hand-in-hand with a general unarousability, which is likely t o lead t o a strong tendency for pregnant females to stay put in dark shelters, and thus avoid exposure t o ULV insecticide applicationsa further reason for their unusual ability t o survive such sprays (Davies, 1978).…”

“…Not only d o they become almost totally immobile for some 4 8 h before depositing a larva, but their circadian rhythm is also much modified: 2 days before larviposition the morning peak of their typical V-shaped flight pattern is over twice as high as normal; virtually no activity occurs for the whole of the day preceding larviposition; and on the day of larviposition, whereas the morning peak of the V is still heavily suppressed, there then occurs a wholly untypical period of high activity in the early afternoon just preceding parturition. Brady & Gibson (1983) postulated that, by preventing heavily pregnant females from flying out into insecticide clouds, this 48 h of inactivity, associated with such females' concurrent photonegativity (Rowcliffe & Finlayson, 1982) might be one reason for the fact that pregnant females are the only members of G.morsitans populations t o survive aerosol non-residual insecticide campaigns (Davies, 1978). The other and perhaps principal reason is that any insecticide picked u p by pregnant females tends to be shunted to the larva via the female's highly lipid 'milk' (see Kwan et al, 1982).…”

Metamorphosis behaviour and regulation in tsetse flies (Glossinaspp.) (Diptera: Glossinidae): a review

“…The clumping of puparia within cavities, beneath objects such as rock overhangs or fallen logs, or in dense thickets, is widely recognized. Pregnant females become intensely active a few hours before parturition (Rowcliffe & Finlayson, 1982;Brady & Gibson, 1983;Denlinger et al 1983), and it is presumably during this time that the female seeks the parturition site. Laboratory experiments suggest a long distance attraction by pregnant females to a dark solid profile and a close range attraction to a shaded region, especially a horizontally orientated shading surface (Rowcliffe & Finlayson, 1981).…”

Influence of temperature changes on larviposition rhythm in the tsetse fly, Glossina morsitans

“…These experiments were all conducted at a constant temperature of 25, 26 or 27°C. Only Rowcliffe & Finlayson (1981, 1982 Correspondence: Professor L. H. Finlayson have investigated the effects of temperature fluctuations on the behaviour of late pregnancy tsetse flies. They demonstrated that as pregnancy progressed there was an increasing tendency to rest in darker sites and that this photonegative response increased with temperature, thus indicating a search for cooler shaded areas.…”

“…The aim was to recreate the situation in the field in which the gravid female is subjected to a sudden rise in temperature, as, for example, when she moves from shade to full sun, or when she alights on hot soil. Apart from orientation responses (Rowcliffe & Finlayson, 1981, 1982 is there any effect on the larviposition behaviour of the fly?…”