i 7 6 



INSECTS 



unprotected point, prompt treatment to destroy the 

 larvae, reduce inflammation and protect the wound, 

 should be resorted to. Carbolated washes or ointments 

 are excellent as protectives, and nothing is better than 

 peroxide of hydrogen to clean and sterilize a suppur- 

 ating sore. 



It is rather an easy step from the sort of elementary 

 parasitism just described, to the simpler forms of at- 

 tack by bot-flies, or (Estrida. Bot-flies in the adult 

 stage are usually large, stout species with a large head, 

 but no functional mouth parts. 

 The adults, therefore, though 

 very highly specialized in some 

 directions, are merely produced 

 to provide for the continuance 

 of the species ; incapable of harm 

 in themselves and, so far as we 

 know, not productive of any 

 distinct good. 



In the simplest forms the 

 adult fly lays an egg on the skin 

 of the animal that serves as a 



host; the larva hatches, bores its way through the skin, 

 enters the tissue and lodges. It increases in size, some- 

 times forms a swelling which may or may not suppurate, 

 and, when full grown, works out through the skin, drops 

 to the ground which it enters to pupate, develops to an 

 adult in due course and the cycle is complete. Bots of 

 this character attack a great variety of animals and even 

 man is not exempt from them. I have personal knowl- 

 edge of such a case and there are enough others on 

 record to make it quite certain that under abnormal 

 conditions some of the species that ordinarily attack 

 other animals may attack man. In tropical regions the 

 attacks on man are much more frequent and are referred 



FIG. 78. Blow-fly, Calliphora 

 vomitoria. 



