SCREW-WORMS AXD OTHER MAG0OT= 



animals are all very similar in ai:>pearance. Ordinarily the differences 

 among them can not be distinguished without a very careful examina- 

 tion under a microscope. Their iiabit of attack, however, indicates 

 with some degree of accuracy whether they are screw-worms or some 

 other species. All have the tisual maggot shape and are nearly white. 

 When newly hatched from the egg they are extremely minute and 

 active, and when full grown they become nearly three-fourths of an 

 inch long. While they have no legs, the body is fitted with minute 

 spines and humps which enable them to crawl and aid them in work- 

 ing their way into an animal or any material upon which the flies are 

 breeding. The head end is rather pointed and provided with two 

 stout black hooks which are used in tearing the food. The lai-ger oi- 

 tail end is provided with two brownish plates through which they 

 breathe. (See fig. 3.) It is this portion of the __ 

 maggot which is seen when one observes a mass of 

 them in a wound. 



THE PUPA. 



The pupa, or resting stage, usually is to be found 

 in the ground. The pupse are somewhat barrel 

 shaped, with the ends rounded. They are about 

 one-third of an inch long. (See fig. 4.) At first 

 they are yellow, but later they turn to a rich broAvn 

 color. When the fly within is mature it splits one 

 end of the shell and crawls out. 



LIFE HISTORY AND HABITS. 



Fig. 4. — Pupa, or 



With the advent of warm weather the flies ap- resting stage, of 

 pear and begin breeding in any available decaying E^niargiT^^^*'"" 

 animal matter. The question of where screw-worm 

 flies breed is one of greatest importance to stockmen. Many are of 

 the opinion that they do not breed in carcasses, but aside from the 

 few which mature in living animals this is the only medium in wdiich 

 breeding occurs. 



The life of the adult fly is comparatively short, ranging from 

 two to six weeks. The flies feed upon various kinds of refuse and 

 to some extent upon the nectar of floAvers. When food is not at 

 hand and the temperature is high the flies usually die in from 24 to 

 48 hours. Eggs are laid in batches from one to four days apart, 

 each mass containing from 40 to 250 eggs. A single female is 

 capable of depositing as many as eight batches of Qg^9, the total 

 number in one case being 1,228. 



