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and the meteorological conditions. As regards the first, Glossina 

 palpalis is found along the banks of rivers where vegetation is dense ; 

 G. submorsitans is seldom found near rivers and is more abundant in 

 the savannah forest and more open country, as well as in the very 

 open country where small water-holes exist, probably because game 

 comes to water there, this species undoubtedly migrating by following 

 herds of game for long distances ; G. tachinoides is an up-country 

 form allied to G. palpalis, and is foimd in similar localities on the 

 higher reaches of the rivers. 



The close association between G. submorsitans and the larger mam- 

 mals all over the Northern Territories of the Gold Coast is very marked, 

 especially in the case of Papio sphinx (dog-faced baboon). The chief 

 factor influencing the numbers of tsetse is, however, that of humidity, 

 the insects increasing greatly in numbers at the beginning of the 

 dry season. G. palpalis is most strongly affected by a hot sun ; 

 G. tachinoides is also affected, though not to the same extent ; while 

 G. submorsitans will follow and attack in the open in the hottest sun, 

 though rarely at night, the same being true of G. morsitans, which 

 has been caught at a temperature of 109° and 112° F. 



A variety of G. palpalis first met with in the upper reaches of the 

 River Gambia, is described under the name pallida, var. nov. 



The food of Glossina appears to consist wholly of blood, the 

 proportion of mammalian to non-mammalian blood varying widely 

 according to the species. G. morsitans seems to be much more depend- 

 ent on mammalian blood than does G. palpalis, while the chief food 

 of G. tachinoides appears to be reptilian blood and that of a large 

 bat which abounds on the banks of the River Volta. The small per- 

 centage of reptilian blood found in G. submorsitans may be due to lack 

 of opportunity and not to preference, since in the open country where 

 G. submorsitans abounds a reptilian fauna is practically non-existent. 



A marked disparity exists in the proportion of the sexes of Glossina, 

 various hypotheses having been advanced in explanation of the fact, 

 such as the size of the river on which the flies are caught, the time of 

 capture, the number of inhabitants in a given area, the season of the 

 year, and meteorological conditions. To these must be added the 

 abundance of game and consequently food, which by causing the 

 retirement of the gorged females gives rise to an apparent disparity. 



Flight experiments conducted with marked individuals of G. tachi- 

 noides yielded the following facts : — The greatest distance covered by 

 a single tsetse was 4 miles ; all seemed to return to the water, as none 

 were caught at a greater distance from the river than the points where 

 they were liberated ; if streams intervened between the place of 

 liberation and the river, the flies made their way down stream to the 

 river ; if the stream bed had shady banks, but no water, the flies 

 congregated there and did not attempt to reach the river ; not a single 

 tsetse was found in the open bush bordering the road, at a greater 

 distance than 200 yards from it ; there was practically no discrepancy 

 in the proportion of the sexes recaptured. 



In wide areas of fly-infested country, such as occur in the West 

 African colonies, systematic trapping of Glossina is impracticable. 

 Trapping with birdlime was found less satisfactory than collection 

 with nets. Substances that acted as deterrents when applied to the 

 clothing of collectors were beechwood creosote and beechwood oil. 



