DIPTEROUS LARV^ 



51 



three months which follow. In its attacks upon man it usually deposits 

 its eggs in the nostrils or mouth while the individual is sleeping. It is 

 especially attracted if the parts are unclean, as from the discharge of 

 nasal catarrh or collections of vomit about the lips. Persons in a drunken 

 stupor are especially liable to attack. For the same reason open sores 

 contaminated by collections of pus or blood are equally attractive to it. 



The fly's greatest injury as a pest to domestic animals in the United 

 States occurs in the Southwest, where cattle are the greatest sufferers 

 from its ravages. In these animals the flies are attracted to wounds of 

 operations, such as dehorning, branding, castrating, etc., and to injuries 

 such as may result from hooking or 

 barbed wire. In fact any open 

 wound or exposed mucous mem- 

 brane, especially if soiled with an 

 odorous discharge, is a favorite seat 

 of attack. 



Upon hatching, the larvae at once 

 proceed to attack the tissues and 

 may rapidly produce a serious de- 

 struction and mutilation. They grow 

 rapidly as they consume the tissues 

 adjacent to them, and in locations, 

 as parts of the limbs where there is 

 little fleshy covering, the bones may 

 be laid bare. 



Protection. — As most of the fatal 

 cases of myasis in man from this 

 cause are due to deposition of eggs 

 in the nostrils while the person is 

 sleeping, the first measure of precaution is to protect from attack by the 

 use of netting. Those sleeping out of doors in infested regions are most 

 exposed, but sleeping rooms should also be thoroughly screened. Open 

 f'.ores and wounds should of course be kept free from collecting discharge 

 and covered with clean, dry dressing. The same precautions as to 

 cleanliness of wounds and exposed mucous membranes applies to domes- 

 iic animals. The vulvsp of cows recently fresh, especially if there has 

 been a retention of the placenta, and the navels of calves offer favorite 

 points for attack and should particularly be guarded. 



Treatment. — Where sores and exposed mucous membranes have 

 already become infested with worms a disinfecting wash, such as a one 

 to three per cent, solution of carbolic acid, should be used. For injection 

 into regions where the maggots have penetrated, the injection of carbolic 

 acid or creolin in about five per cent, strength will destroy worms with 

 which it comes in contact. Chloroform diluted to a strength of about 



Fig. 26. — Compsomyia macellaria — en- 

 larged (after Osborn, from Francis, Bui. 

 No. 5, Bureau of Entomology, U. S. Dept. 

 of Agr.) . 



