POSSIBLY VARIABLE. 25 



Further observations, however, on the reproduction of Tsetse-flies 

 ^re urgently needed, particularly with a view to discovering 

 whether the process is the same in all the species. From the 

 reproductions of photographs given by Colonel Bruce in his 

 " Further Report," one of which represents a fly in the act of 

 parturition, the species which formed the subject of his investi- 

 gations would appear to have been Glossina pallidipes, Austen^ 

 rather than Gl. morsitans, Westw. It is therefore necessary 

 to point out that, from what we know of the life-history of other 

 Muscidse, it must not be taken for granted that all species of 

 Glossina necessarily produce a full-grown larva, which imme- 

 diately assumes the pupal stage, since in some genera there is a 

 remarkable diversity in the mode of reproduction even in the 

 case of closely allied species. Thus, according to Portchinski, 

 the common European Mesembrina meridiana^ Linn., is vivi- 

 parous, while Mesembrina resplendens, Wahlbg., and M. mystacea, 

 Linn., lay eggs ; and whereas Musca domestica, Linn., lays 

 from 120 to 160 small eggs, Musca corvina, Fabr., either lays 

 9,bout twenty-four large eggs, provided with peculiar appendages, 

 or, as was found by Portchinski to be the case in summer in the 

 Crimea, produces a single full-grown larva.* 



so-called " sheep-tick." In all of these the female produces hut a single 

 full-grown larva at a hirth. While within the body of the mother the 

 larva is nourished by the secretion of special glands, and assumes the 

 pupal stage immediately after extrusion : unlike that of the Zululand 

 Tsetse, the Hippoboscid larva is incapable of movement. Bruce's descrip- 

 tion shows that the larva of the Zululand Tsetse-fly must be very similar 

 in appearance to the newly-extruded larva of Hippobosca equina, which is 

 yellowish white in colour, with the terminal segment deep black. The 

 latter also exhibits two prominences, which, however, although distinct, 

 are not so pronounced as in the larva of the Zululand Tsetse. The mature 

 pupa of Hippobosca is dark brown, but shows no distinct trace of segmenta- 

 tion. In Hippobosca camelina, Savigny, which is parasitic on camels in 

 Northern Africa and in Asia, and is a much larger species than H. equina, 

 the protuberances at the posterior end of the pupa are scarcely distinguish- 

 able, although the dull black area is just discernible. In Oxypterum 

 pallidtim the pupa shows faint traces of the annuli belonging to the larval 

 integument, while the " black hood " takes the shape of a flat rosette- 

 shaped plate, devoid of prominences. 



* Cf. Baron C. E. Osten Sacken, "On Mr. Portchinski's publications 

 on the larvce of Muscidse " : Berliner Entomologische Zeitschrift, Bd. xxxi. 

 (1887), pp. 17-28). According to Portchinski, Musca corvina in Northern 

 Europe deposits on dung about twenty-four large eggs with peculiar 

 appendages. In the Crimea in early spring its reproduction takes place in 

 the same way ; but towards the end of spring, and in summer almost 

 exclusively, Portchinski found a single very large egg within a matrix-like 

 expansion in the body of the female. From this egg a larva was 

 developed which grew within the body of the mother, but passed directly 

 from the first to the third, or final stage {Cf. Osten Sacken, loc. cit., p. 26). 

 Another remarkable instance of larval development within the body of the 



