52 DISTRIBUTION OF GLOSSINA MORSITANS. 



Collection by its author, I am satisfied that it is impossible to 

 regard G. submorsitans, Newst., as specifically distinct from 

 G. morsitans, Westw., and that it is in reality nothing more 

 than a form or race of the latter. As will shortly be shown, 

 G. morsitans is the most widely distributed of all the Tsetse-flies, 

 and it is, therefore, not surprising to find that even morphological 

 characters are not absolutely identical in the case of specimens 

 from localities situated at the opposite extremities of its area, 

 and separated from one another by some thousands of miles. 

 The form submorsitans has hitherto been found in West Africa 

 and the Anglo-Egyptian Sudan, and it is of course possible that, 

 e.g. a male from Northern Nigeria belonging to this form might 

 be incapable of mating with a female of the typical race of 

 G. morsitans from the Bechuanaland Protectorate. Still, if the 

 area of G. morsitans could be traversed from end to end, starting 

 from the Bechuanaland Protectoi-ate or the North-Eastern 

 Transvaal and proceeding to Northern Nigeria or the Anglo- 

 Egyptian Sudan, it is not unreasonable to suppose that it would 

 be found that the form submorsitans constitutes, as it were, one 

 end of a chain of groups of interbreeding Tsetse-flies, of which 

 the other extremity would be represented by typical Glossina 

 morsitans, Westw. 



As indicated in the description printed above, the dark bands 

 on the abdomen of G. morsitans are subject to much individual 

 variation as regards the extent to which they are developed. 

 The external characters mentioned by Mr. Newstead as serving 

 to distinguish his G. submorsitans from G. morsitans, Westw., 

 which are entirely derived from the abdominal bands, have been 

 carefully tested by examining the material in the National 

 Collection, and comparing it both with the types of the form 

 submorsitans and with typical specimens of G. morsitans, Westw., 

 with the result that in each case the character selected has 

 sooner or later proved unreliable and ultimately invalid. 



DisTRiBUTiox OF G. morsitans, Westw. 



Glossina morsitans, Westw., once regarded as an exclusively 

 South African species, is unquestionably the most widely dis- 

 tributed of existing Tsetse-flies, since its range extends from 

 Senegambia (about 16° N.) in the north-west, to Southern 

 Kordofan (about 12° N.) and Southern Abyssinia in the north- 

 east, and thence southwards to the Bechuanaland Protectorate 



