ANIMAL PARASITES OF CATTLE. 507 



be held for several minutes in order to insure the continued action of 

 chloroform. Instead of chloroform, gasoline may be used, and 

 carbon tetrachlorid is said by some authorities to give good results. 

 Finally, the dead or dying maggots may be removed with forceps, the 

 wound washed with a weak carbolic or cresylic acid solution, and 

 painted with pine tar to reduce the chances of further attack by fhes. 

 Finally the wound should be dressed with a carbolic or cresylic oint- 

 ment to promote healing and thus prevent further infection, or the 

 wound may be painted with pine tar. Dipping in the arsenical dips 

 used for destroying cattle ticks is a convenient method of treatment 

 if many animals are involved. 



GRUBS, WARBLES, BOTS. 



Ox warbles are whitish or, when full grown, dark-colored grubs or 

 maggots that develop from the eggs deposited on the hairs of cattle 

 by certain fhes known as warble 

 flies . In the United States there are 

 two species of ox-warble flies, tech- 

 nically known as Hypoderma linea- 

 tum and Hypoderma hovis. These 

 flies somewhat resemble bees in 

 their general appearance, but hke 

 all fhes have only two wings. 



The first named, H. lineatum, is 

 commonly called the heel fly and 

 is more generally distributed over 

 the United States than the other 

 species. The tail has a distinctive 

 reddish-orange color and the legs 



are rough and hairy. This fly com- ^'^- 5.-Screw-wonn fly ( Chrysomyia macellaria). 

 , °. . . , *^ T Enlarged. (From Bureau of Entomology.) 



monly deposits its eggs about the 



coronet, whence the name of heel fly, and on the fetlocks, knees, and 

 hocks. CWhen cattle are resting, eggs are deposited along the line of 

 contact of the body with the soil. ,) Cattle are frequently indifferent 

 to the activity of this fly in depositing its eggs. Commonly 8 to 10 

 eggs, sometimes as many as 14, are attached to a single hau'."^; 



In the United States the other warble fly, H. hovis, has been foimd 

 only in the North (New England, New York, Pennsylvania, Maryland, 

 Mchigan, Iowa, Missouri, and Wasliington) and has not yet been found 

 in the Southern States. The tail is orange-yellow, lighter in color 

 than that of the other species, and the legs have but few hairs. This 

 fly commonly deposits its eggs on the outside of the hind quarters 

 and above the fetlocks when the animals are moving, or lower down 

 if they are quiet. Cattle are usually much disturbed by the activity 



