CHAPTER II. 



DISTINCTIVE CHARACTERS AND GEOGRAPHICAL DISTRIBUTION OF THE 

 VARIOUS SPECIES OF TSETSE-FLIES. 



In this chapter we shall confine ourselves to a consideration of the 

 different species of Glossina, describing the external characters by 

 means of which they may most easily be distinguished, and furnishing 

 some particulars as to their geographical distribution. For the 

 purpose of this short account Austen's work, referred to above, has 

 been followed, with modifications necessitated by later discoveries. 



GROUP I. 



Glossina palpalis, Rob.-Desv. (Plate I, Fig. 1). This species is one 

 of the most important of its genus, since it is the disseminator of 

 Trypanosoma gambiense, the cause of sleeping sickness in West and 

 Central Africa. 1 



The abdomen in G. palpalis is "clove-brown or blackish-brown ; 2 

 the thorax usually paler, with dark brown markings on a greyish 

 ground .... first segment " of the abdomen, " and a median 

 triangular area on the second .... buff-coloured or cinereous, 

 the pale triangle continued backwards as a narrow, more or less well- 

 defined median stripe, usually reaching at least as far as the hind 

 margin of the fifth segment ; lateral margins of the segments from the 

 second onwards grey, expanded on the apical angles into triangular 

 markings ; extreme hind margins of the segments from the second to 

 the sixth usually narrowly pale or grey ; seventh segment .... 

 entirely grey .... Femora in typical race more or less mouse- 

 grey, greyish-brown, or dark slate-coloured ; tibiae, extreme tips of 

 femora, and first three joints of front and middle tarsi buff or ochraceous- 

 buff, hind (or middle and hind) tibiae sometimes infuscated in $ ; 

 hind tarsi blackish-brown or clove-brown above ; wings strongly tinged 

 with sepia-brown, but not quite so dark as in G. caliginea, Austen " 

 (Austen. See Plate I, Fig. 1). 



" The area occupied by Glossina palpalis," writes Austen, " includes 

 the whole of West Africa, from the mouth of the Senegal River (about 

 16 N.) to Angola (where the variety wellmani apparently predominates), 

 and extends eastward into the southern Bahr-el-Ghazal," thence 

 reaching the River Omo, which falls into the northern end of Lake 

 Rudolf. " Proceeding southward, the eastern boundary of the species 

 follows the valley of the Nile and includes the eastern shores of Lakes 

 Victoria " (in Kenya Colony and Tanganyika Territory) " and Tan- 

 ganyika " 3 (in Tanganyika Territory), " and their affluents ; from the 

 southern end of the latter lake the boundary trends south-west, approxi- 

 mately following the frontier between north-eastern Rhodesia and 

 Belgian Congo, and passing through the Katanga district of the latter 

 country into Angola. G. palpalis appears not to occur on Lake 



1 Recent investigations carried out in Nyasaland and Northern Rhodesia 

 have shown that in those regions sleeping sickness, caused by Trypanosoma 

 rhodesiense, is transmitted by Glossina morsitans. 



2 In the case of many species of Tsetse-flies the abdomen, if containing blood, 

 becomes greatly darkened in colour. 



8 On the western shore of Lake Tanganyika, in the Kasongo district of Belgian 

 Congo, the species also occurs in abundance (Rodhain. 115). 



