XVIIl] STOMOXYS 355 



nucleate masses are produced, sometimes filling the whole field 

 of the microscope (Fig. 80). 



The life history of this parasite in its intermediate host, 

 Glossina morsitans, has not yet been worked out. Its extreme 

 pathogenicity in monkeys is very remarkable and suggests 

 that T. simicE is a species that has only recently become adapted 

 to its present mode of life. 



LITERATURE. 



Bruce, Harvey, Hamerton, Davey and Lady Bruce (191 2). Proc. Roy. 



Soc. B, vol. Lxxxv. p. 477. 

 Kinghorn and Yorke (1912). Ann. Trop. Med. and Parasit. vol. vi. 



pp. 301-315 and 317-324. 



CHAPTER XIX 



STOMOXYS 



General description. The members of the genus Stomoxys 

 may be distinguished from other blood-sucking Muscidae by 

 the following characters : 



The proboscis protrudes horizontally in front of the head 

 and is pointed towards its anterior extremity. The maxillary 

 palps are cylindrical and slender, less than half the length of 

 the proboscis. The first longitudinal vein opens into the wing 

 about mid-way along its length, almost opposite the small 

 transverse vein. The first posterior marginal cell opens widely 

 at the tip of the wing. Between the posterior transverse vein 

 and the margin of the wing the fourth longitudinal vein is 

 arched like a bow with the concavity facing the third longi- 

 tudinal vein (Fig. 81). 



The flies belonging to this genus are all moderate sized 

 (5 to 7 mm.) dull-coloured insects that generally feed on the 

 blood of cattle. They closely resemble the house-fl}^ [Musca 

 domestica) in general appearance, but may be readily distin- 

 guished by the presence of the proboscis, and also Stomoxys 

 rests with its wings widely divergent whilst in Musca they are 



23—2 



