25 



of larvae should not continue throughout the year, though he suggests 

 that the height of both the wet and dry seasons may be unfavourable 

 to the development of the pupae." 



LARVA. We give below a description of the larva of three species 

 of Tsetse-flies, G. palpalis, G. morsitans and G. brevipalpis. 



An excellent illustrated account of the external characters and 

 internal anatomy of the larva of G. palpalis has been furnished by 

 Dr. E. Roubaud (96). The following details, from which, owing to 

 considerations of space, all reference to internal anatomy is necessarily 

 omitted, are taken from this description. 



The new-born larva, which measures from 7 to 8 mm. in length by 

 2 -8 mm. to 3- 5 mm. in breadth, is a yellowish-white, cylindrical 

 maggot, with a deep black posterior extremity bearing the rounded 

 terminal protuberances [i.e., the "tumid lips" (Austen) or "poly- 

 pneustic lobes" (Newstead. 108) 1 ]. Crawling very actively about, 

 the larva undergoes constant changes of shape as the result of undu- 

 latory contractions ; in this way the anterior region of the body some- 

 times swells out suddenly, so as to act like a battering-ram. Thanks 

 to these special movements, coupled with great plasticity, the creature 

 is able not only to burrow rapidly, but also to insinuate itself into the 

 smallest fissures beneath the actual surface of the soil. According 

 to the author referred to, this mode of progression is a special 

 characteristic of the Glossina maggot, and is not found in other 

 Dipterous larvae. 



" Including the pseudo-cephalic region and the caudal callosities," 

 continues the French author, " the number of visible segments in the 

 larva of G. palpalis is thirteen. The twelfth or anal segment is 

 scarcely distinguishable on the upper surface, where it is represented 

 by a narrow band, squeezed between the chitinised border of the 

 thirteenth segment and the posterior margin of the eleventh ; on the 

 ventral side it is much more conspicuous, and exhibits in the median 

 line, towards the posterior margin of the segment, a small and very 

 inconspicuous punctiform depression, with a blackish, chitinised 

 margin, which represents the vestigial anus. This orifice, which 

 occupies the same position and exhibits the same degree of reduction 

 as in the larvae of the Diptera Pupipara, was misunderstood by Stuhl- 

 mann, the only author who has hitherto studied the organisation of 

 Glossina larvae in any detail. 



" The cephalic region, in fully extended larvae, narrows perceptibly 

 from the fourth segment onwards. The head, as in all Dipterous 

 larvae of the acephalous type, is excessively inconspicuous. Lying 

 concealed towards the centre of the second segment, its limits are 

 difficult to distinguish, but it is nevertheless recognisable as being 

 divided into two lobes by a slight anterior and ventral furrow, each of 



1 Nine years after the publication of the work of M. Roubaud it was shown by 

 Newstead (108), in a paper of remarkable interest, that these terminal pro- 

 tuberances are respiratory organs, which function during the intra-uterine 

 life of the larva ; and that the "innumerable papillae," which cover the outer 

 surface of the lobes and give them their characteristic appearance, are really 

 minute stigmata or openings communicating with the larval tracheal system. 

 Newstead, who therefore terms these protuberances " polypneustic lobes," 

 shows that closely similar structures are found in the larvae of Hippoboscidae, 

 as well as apparently in other Dipterous larvae, whose identity and systematic 

 position have yet to be determined. In the case of Tsetse-fly larvae, the number 

 of stigmata in each polypneustic lobe is very large in the larvae of G. palpalis, 

 according to Newstead, probably more than five hundred. 



