176 



DIPTERA. 



around the edges of its segments, and provided with six 

 spines at its hinder extremity : it comes to the surface of 

 the ground when about to be transformed into the perfect 

 fly, showing its body half out of the earth. 



The Tsetse, described by Dr. Livingstone, is perhaps 

 the most formidable of the insect race ; it is not much 

 larger than the common house-fly, and is nearly of the 

 same brown colour as the honey-bee. The bite of this 

 poisonous insect is certain death to the ox, horse, and 

 dog ; but is perfectly harmless to man, wild animals, and 

 even calves as long as they continue to suck. Its poison 

 is inserted by the middle prong of three portions, into 

 which the proboscis divides, which it plunges deeply into 

 the skin exactly in the same manner as a gnat, and then 

 sucks the blood until it is filled. A slight itching irrita- 

 tion follows, but not more than that produced by the ' 

 bite of a mosquito. In the ox this same bite produces 

 no more immediate effects than in man ; but in a few 

 days, the poor creature bitten, sickens and dies. This 

 terrible insect is, fortunately, confined to certain parts of 

 Africa. 



The Chameleon Flies (Stratyomys), so called from the 

 variety of their colours, are a very harmless race, remark- 



r\ 



FlG. 136. LARVA OF STRATTOMYS. 



able on account of the phenomena attending their meta- 

 morphosis. Their larvae are to be found in ditches abound- 

 ing with filth ; their bodies are long, flattened, and tapering 

 towards each extremity, their skin is of a horny or leathery 

 texture, and their tail is surrounded by long, plume-like 

 hairs, that encircle the orifice through which they breathe. 



