23 



CHAPTER III. 



REPRODUCTION OF TSETSE-FLIES. 



" The mode of reproduction in Tsetse-flies first discovered by Sir 

 David Bruce, during his classical investigations in Zululand in 1895-96 

 is extremely remarkable, since, instead of laying eggs as do the 

 majority of Diptera, the pregnant female produces at each birth a 

 single full-grown larva, which, while retained within the oviduct of 

 the mother, is nourished by the secretion of special glands, and on being 

 born crawls away into some hiding place and immediately changes 

 into a pupa" (Austen). 



In the following sections we shall pass briefly in review the different 

 stages of reproduction in Tsetse-flies, in so far as it is possible to describe 

 them at the present time, in the light of recent discoveries, made by 

 various investigators, chiefly in Rhodesia. 



COPULATION. The act of copulation, in the case of captive G. 

 morsitans. has been described by Dr. Allan Kinghorn (79). " Copu- 

 lation," writes Dr. Kinghorn, " was frequently observed between the 

 captive flies, more often after feeding. During this process the mates 

 are firmly locked together, and refuse to separate even on violent 

 shaking of the tube. It continues for several hours, as a rule, and on 

 a few occasions two flies which coupled in the afternoon were found 

 the following morning still fastened together. Coupling may occur 

 more than once between the same two flies." As regards G. brevi- 

 palpis, Dr. J. B. Davey, writing of the habits of this species in 

 Nyasaland, says : " One pair was observed in coitu on a tree at 

 midday, the terminal abdominal segment of the male, which was on 

 the back of the female, being curved round the terminal segment of 

 the latter ; at intervals the male made a rapid vibratory movement 

 of the wings : the wings of the female were slightly abducted from the 

 body. They were so firmly locked that one was able to capture and 

 kill them without causing separation." 



As to the period at which copulation occurs, it is stated by Dr. 

 Roubaud (1190), who observed the behaviour in captivity of G. 

 tachinoides in Dahomey, that, just as in the case of G. palpalis under 

 similar conditions, coupling in these flies takes place immediately 

 after emergence from the pupa. Dr. Roubaud, on the other hand, 

 never witnessed the copulation of G. longipalpis in captivity. 



It will be gathered from the foregoing that present knowledge as 

 to the act of copulation is still very imperfect, while with regard to 

 certain species we know nothing about the matter at all. 



GESTATION. As has already been stated, a pregnant female Tsetse- 

 fly produces at each birth a single fully developed larva, which, while 

 retained within the oviduct of the mother, is nourished by the secretion 

 of special glands. Towards the close of the period of intra-uterine 

 life, the larva almost completely fills the abdomen of the mother, and 

 is visible by transparency through the abdominal wall, as a dirty 

 yellowish-white, oval body, with prominent black lips. The latter 

 already show very distinctly, several days before birth. 



BIRTH OR EXTRUSION OF THE LARVA. Dr. Kinghorn (79) states 

 that, in the case of G. morsitans, " The extrusion of the larva is 

 accomplished very quickly, and the maggot commences to crawl 

 about as soon as it is born." 



