510 DISEASES OF CATTLE. 



possible, as in the case of several other parasites, that both modes of 

 infection may occur and that the larvae 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. In*espective of the mode of infec- 

 tion, the larvae 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. 

 FinaUy, 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 wliich it 

 feeds. By spring 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 discovered that a second species of warble fly 

 {Eypodenna hovis) common in Europe is of not uncommon occur- 

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

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

 all of the one kind. The general appearance, life history, and effects 

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

 form. 



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

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

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

 butchers as "hcked beef." 



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

 mated at $35,000,000 to $50,000,000 a year, at the least, and may 

 amount to considerably more. 



Treatment for warhles. -^Dumig the winter and spring examine 

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

 backs of the animals the sweUings marking the location of the grubs 

 may be readily found. Pressure properly apphed to the swelhngs 

 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 

 slender forceps inserted into the opening of the warbles, and a still 

 more certain method of removing them, particularly if the lumps are 

 still very small, is to cut into the swelhngs with a sharp knife or 

 bistoury, after which they may be pressed out. Care should be taken 



