236 THE INSECTS. 



Stomoxys calcitrans. These greatly resemble the common 

 housefly in size and shape. They can be easily distinguished by the 

 black, piercing proboscis extending beyond the head. There are 

 longitudinal stripes on the thorax and spots on the abdomen. The 

 proboscis on examination will be seen to be bent at an angle near its 

 base. The palps are short and slender. The wings diverge widely. 

 The genus Stomoxys includes vicious biters. This is the fly which 

 comes into houses before a rain, and which has given the common 

 housefly the reputation of biting before a rain. Stomoxys may be 

 implicated in transmitting surra (Trypanosoma evansi). 



The horsefly (Haematobia irritans) rarely bites man. In these the 

 palpi are much longer than in Stomoxys. 



Glossina palpalis. This is the tsetse fly that is responsible for 

 the transmission of human trypanosomiasis and the later stage of the 

 disease, sleeping sickness. The tsetse fly is a small brownish fly about 1/3 

 of an inch long. The proboscis extends vertically and has a bulb at its 

 base. The arista is plumose only on the upper side. The wings are 

 carried flat, closed over one another, like scissor blades. The most 

 characteristic feature of the tsetse fly is the way the fourth longitudinal 

 vein bends up abruptly to meet the oblique transverse vein. In 

 Stomoxys, the wings separate; in Hsematopota they just meet, and in 

 Glossina they cross. The tsetse fly does not lay eggs, but gives birth to 

 a single full-grown larva which immediately becomes a pupa. Glos- 

 sina morsitans transmits the cattle trypanosomiasis disease, nagana. 



Auchmeromyia luteola. This is an African fly, the larva of 

 which is known as the " Congo floor maggot," and is a blood sucker. 

 The larva is of a dirty -white color and about 2/3 of an inch long. It 

 crawls out at night and feeds on the sleeping natives. This is the only 

 known instance of a blood-sucking larva. 



Calliphora vomitoria and Lucilia caesar. These are flies with 

 brilliant metallic-colored abdomens, commonly called blue-bottle flies. 

 They deposit their eggs on tainted meat and in wounds. Many cases 

 of obscure abdominal trouble are probably due to the larvae of these 

 flies. Intestinal myiasis is undoubtedly of greater importance than has 

 been thought. The larvae, with hook-like projections anteriorly and a 

 ringed body, can easily be recognized in the faeces. They have been 



