62 WARBLE FLIES. 
animal in a clumsy manner. For this reason, they seem to 
recognize it as an enemy and become very nervous and excited, 
racing pell-mell about the fields 
in an attempt to escape from it. 
It was formerly thought that 
the fly inserted its egg in the 
skin on the back or placed the 
eggs so that the grubs could 
work their way through the 
ond 
Fic. 6. Vertical ssction of hide and subjacent skin, but this 1s now disproved. 
tissue. showing oxwarble in position, Diagra- ra 
matic. Courtesy of Country Gentleman. When the young grubs hatch 
from the eggs, they are licked up by cattle and carried into the 
mouth. From there they migrate into the gullet and bore into its 
walls. Part of their development takes place here. Some observers 
have found them in the spinal canal and pancreas. How the migra- 
tion takes place we do not know, but about January they suddenly 
appear under the skin on the back, forming swellings or tumors. A 
small opening is made through the hide, which is enlarged as the 
grub grows, until in spring it may have a diameter of one-quarter 
of an inch. The posterior end of the grub is forced against this 
opening and it is thus able to breathe and to discharge its excrement 
to the exterior. By spring or early summer, the grub is fully grown 
and working its way through the opening in the hide, falls to the 
ground, into which it burrows and transforms to the pupal stage. 
About a month after this the fly emerges. 
The flesh in the vicinity of the grub becomes slimy and of a 
greenish color and is known as “licked beef.” This is another 
cause of loss as the consumer is apt to be prejudiced against the 
use of such beef. 
The treatment for warbles is fairly easy. In late winter and 
spring, examine the cattle for the presence of the tumors. They 
can be readily felt by passing the hand over the back. The size 
of the tumor can be imagined when it is known that the full-sized 
grub may measure 144 inches in length. If the grubs are full- 
grown and nearly ready to emerge, they can be forced out through 
the opening in the skin with very slight pressure. If they are 
not full-grown, it is more difficult to remove them by squeezing, 
but frequent examinations will make it possible to secure each 
one. Care must be exercised to crush each grub as soon as 
removed so as to avoid the possibility of any reaching the soil 
and eventually producing adult flies. 
