167 



the other hand two species of Hippobosca are said to be capable of 

 disseminating a trypanosomiasis of cattle in the Transvaal,* and one 

 of these species has been associated, though without proof or 

 anything in the shape of experimental evidence, with a form of 

 anthrax affecting horses in a part of Cape Colony. 



Genus HIPPOBOSCA, Linnaeus. 

 Fauna Suecica, Ed. II., p. 471 (1761). 



PLATE XIII., FIGS. 98-100. 



The easily recognisable species belonging to this genus, which, 

 with one remarkable exception (Hippobosca struthionis, Janson, 

 Plate XIII., fig. 98), are all parasitic upon mammals (horses, 

 donkeys, camels, cattle, or dogs), have a horny appearance so far as 

 regards the anterior half of the body, which is alone visible in the 

 living insect under normal conditions. The thorax, which varies 

 in coloration from yellowish- or reddish-brown to clove-brown, is 

 conspicuously spotted or otherwise marked with yellow, and, as may 

 be seen from the figures on Plate XIII., these markings afford a 

 ready means of distinguishing the species. The abdomen, normally 

 concealed by the closed wings, which, as in the Tsetse-flies, lie flat 

 one over the other like the blades of a pair of scissors, and project 

 a long way beyond the end of the abdomen (see figs. 98 and 99), 

 is leathery, sac-like, and devoid of distinct segmentation ; in the 

 gravid female shortly before parturition, as represented in fig. 100, 

 it is enormously distended. The wings have a brownish tinge, and 

 the strongly developed veins are crowded together into a small area 

 including and adjacent to the proximal three-fourths of the costal 

 margin ; below and beyond the veins the wing-membrane is 

 conspicuously rilled, i.e., thrown into narrow, oblique ridges and 

 furrows. The legs are powerful and adapted to their function of 

 clinging to the hair or feathers of the host, the tarsal claws, which are 



* See p. 176. 



