516 DISEASES OF CATTLE. 



Ak ;v result of recent studies by a arious investigators it appears 

 that the tiny gi'ul-is, newly hatched from the eggs, may gain entrance 

 to the body )jy penetrating directl^r tlirough the skin. Many ob- 

 ser\ers, howexer, have held that the eggs or newly-hatched larvae 

 are taken into the mouth by the cattle licking themselves. It is 

 possible, as in the case of several other ])arasites, that both modes of 

 infection may occur and that the lar^-a- may gain entrance to the 

 body either by penetrating the skin or by being swallowed. From 

 the evidence at present available it seems likely that the usual mode 

 of entrance is through the skin. Irrespective of tlie mode of infec- 

 tion, the larv;e evidently wander extensively through the tissues of 

 the body, developmental stages being found in considerable numbers 

 in the wall of the esophagus during the fall of the year. They have 

 also been found in the spinal canal and in various other locations. 

 Finally, about January they appear beneath the skin of the back, 

 forming the well-known swellings. The posterior end of the grub is 

 near the small opening in the hide, through which the grub breathes 

 and discharges its excrement, and through which, when its develop- 

 ment is complete, it finally escapes. The anterior end of the grub is 

 at the bottom of the tumor, where the mucus collects upon which it 

 feeds. By sj^ring or early summer the grub is full grown and forces 

 its way out of the skin, falling to the ground, into which it burrows 

 for a short distance and transforms into the pupal stage. In about a 

 month the mature fly emerges. 



It has lately been disco\ered that a second species of warble fly 

 (nypoderma hovis) common in Europe is of not imcommon occur- 

 rence in Canada and the northern part of the United States, whereas 

 it was formerly suppdsed that the ox warbles of this country were 

 all of the one kind. The general appearance, life history, and eft'ects 

 ( f the European species are much the same as those of the American 

 form. 



Grubs weaken cattle, cause them to fall olf in flesh and milk, and 

 decrease the value of the hide. The beef in the immediate vicinity 

 cf a grub becomes slimy and of a greenish color, and is known to the 

 butchers as " licked beef." 



The total loss to this country on account of the warble fly is esti- 

 mated at $35,000,000 to $^0,000,000 a year, at the least, and may 

 amount to considerably more. 



Treatment for wv/r/Vcv.— During the winter and spring examine 

 the cattle for the presence of warbles. By passing the hand over the 

 backs of the animals the swellings marking the hx/ation of the grubs 

 may be readily found. Pressure properly applied to the swellings 

 will cause the grubs to "pop out" if they have reached a late stage 

 of development. They may be more easily removed by means of 



