INSECTS. 





might otherwise prove dangerous to the health of mankind The 1 .low- 

 flies are especially fond of depositing their eggs upon meat or cheese, and 

 are regarded as even more of a nuisance than the 

 smaller house-flies. 



The celebrated tse-tse fly of tropical Africa is 

 something like the blue-bottle in shape and size, 

 but it is a far more dreadful pest than any insect 

 among us. Its mouth parts (shown on the left of /^ 

 our cut) are strong, sharp, piercing instruments with 

 a poison-gland at the base, and the punctures of 

 this are followed by death in the case of cattle, 

 horses, sheep, and dogs, but in the case of man and 

 many other animals they are harmless, or productive of no more severe 

 consequences than the bite of a mosquito. In the case of an ox, for 

 instance, there is no immediate effect; but in the course of a week a >< in- 

 forms around the puncture, and then the nose begins to run, and swellings 



Fig. 25.?. — Blow-fij < 

 phora vomitoria I, enlarged 



twice. 



Fig. 254. — Tse-tse fly (Glossina morsitans), enlarged, with magnified views of the head and 



antenna. 



occur under the jaw. The animal now grows thin and weak, ami in the 

 course of a few months dies, sometimes with staggering and blindness, as 

 if the poison affected the brain. 



If a swarm of these animals attack a horse at once, the death is more 

 speedy, sometimes occurring within a week. After death almost every 

 tissue in the body shows signs of disease; and as yet there is nothing 

 known which will avert a fatal result in case any of the animals men- 

 tioned above be bitten. Bv some the tse-tse is identified as the fly which 

 caused the fourth of the plagues of Egypt, but the evidence on this point 

 is far from conclusive. 



The cheese-mite, or skipper, is a familiar form, the larva of a small fly. 

 The larvae jump about in the most lively manner, although they have n<> 



