J. A. Boyle

A promising method for rearing Glossina austeni (newst.) on a small scale, based on the use of rabbits' ears for feeding

Abstract By manually applying cages to the ears of ordinary rabbits and coaxing the tsetse flies to feed, we have for the first time approached the full reproductive potential of G. austeni and reared an insect which does not seem to be physically inferior to that found in nature. The tedious coaxing process has been overcome by strapping cages to the ears of lop-eared rabbits, but at a small loss in pupal weight. Our preliminary findings suggest that a method has been found which should enable a research worker to keep his own small colony of tsetse and achieve an excellent survival rate for trypanosome transmission experiments.

A method of maintaining Glossina austeni newst. singly, and a study of the feeding habits of the female in relation to larviposition and pupal weight.

To permit detailed study of individual tsetse, either as insects or as the vectors of trypanosomiasis, a method has been devised which resulted in excellent survival and reproduction when tested on females or Glossina austeni Newst. Each mated female was maintained in asmall cage comprising a stainless steel frame covered with non-absorbent black Terylene netting through which the larvae and faeces fell into a tray. Each cage was applied daily to the ear of a rabbit, and records were kept of the number of feeds, time taken to feed, numbers of larvae produced, lengths of interlarvel periods and weights of pupae. The following conclusions are tentative as they are based on detailed studies of only eight females. Five of these produced larvae regularly at 8½- to 9-day intervals. Ninety-six interlarval periods were investigated. Although the mean interval between meals was two days, the flies tended to fast before larviposition and to engorge repeatedly afterwards. Among nearly regular breeders, failure to larviposit did not seem to interrupt the normal feeding rhythum: the reproductive rhythum later re-integrated with the feeding ehythum. A tendency to deviate from the normal feeding pattern either by too frequent feeding after larviposition or by prologation of the fasting period before larviposition, may possible be related to pemature death, but flies which tend to feed on the day before larviposition centainly risk death from pupation in utero —a condition found in 5 per cent. of dead rabbit-fed flies; the complex of pressures which lead to this condition is described. Limited data suggest that females which live to a great age enter a post-productive period when about 6½ month old; the feeding pattern breaks down completely, the fly fasting for periods of up to 11 days, or even longer in the immediate pre-death period. The maximum output of reasonably sized pupae is probably about 20 for G. austeni . Pupal weight increased until the parent flies were about 90 days old, but there was much individual variation; thereafter the weight remained high, but among very old dlies it fell towards the end of reproductive life. Certain individuals tended to produce heavy pupae, a characteristic probable associated with the size of the fly and the total weight of blood taken up in each interlarval period—not with the frequency of feeding; a very infrequent feeder may, however, produce underweight pupae at irregular intervals.

Pupal weight in relation to female age in Glossina austeni Newst.

All of the pupae, totalling over 3,750, produced by 320 laboratory-bred females of Glossina austeni Newst. allowed to feed from rabbits’ ears, were weighed soon after deposition. Pupal weights were relatively low initially but increased during the first 30 days of the females’ productive life, were high during the next 100 days or so and thereafter declined to less than the initial level.