ANIMAL PARASITES. 143 



The larvae of this fly are also common 



lA 



Cyaniven- 



parasites. They are distinguished from 



TRis ^^^ larvae of noxialis by having no fine 



spines on segments two and three, but a 

 row of strong hooks projecting from the hind margin of 

 segments four to seven (Blanchard). 



Compsomyia macellaria is known through- 

 CoMPsoMYiA out America, but cases of myiasis due to its 

 Macellaria. larvae are only common in the warmer por- 

 tions. The larva is known as the '^ screw 

 worm." The bot-fly itself has a reddish-brown head, 

 a bluish-green thorax and abdomen, and the thorax 

 is further distinguished by three longitudinal black 

 stripes. The eggs are deposited upon the skin, where 

 they quickly hatch, and the larvae then work their way 

 into the subcutaneous tissues and produce abscesses. 

 But here and there eggs are laid in the nostrils of individ- 

 uals asleep. In this situation the growing worms pro- 

 duce a terrible state of affairs, since in their burrowings 

 they may destroy all the tissues of the soft palate and 

 posterior pharynx, and may even lay bare the hyoid 

 bone. As many as three hundred maggots have been 

 discharged from the mouth and nose of a single indi- 

 vidual. 



This, the common blue-bottle or flesh-fly, 

 Sarcophaga occasionally lays its grubs in old ulcers, 

 Carnaria. which then have the appearance of ^ liv- 

 ing," that is to say, the maggots are as 



