20 BOARD OF AGRICULTURE. 
some writers, they pierce the skin, by means of their peculiar 
gimlet-like ovipositor ; but others deny this, and say that the 
eggs are merely attached to the skin, and that the young 
larve, which very soon hatch, eat their way in. At any rate 
Figure 22. Figure 23. 
the cattle are often greatly alarmed by their attacks, and run 
frantically about, sometimes even taking to the water for 
safety, which would hardly be the case unless they had suf- 
fered pain from their attacks. Working oxen, when thus 
attacked, sometimes cause serious trouble. 
The larve having entered the skin increase the size and 
depth of their burrows as they grow larger, but always keep 
up an opening with the exterior, and keep the posterior end 
of the body, in which the breathing pores are situated, near 
this opening to get air. In this way they cause, by the irrita- 
tion and inflammation that they produce, tumors or abscesses 
of considerable size beneath the skin, and live upon the 
matter formed by the inflammatory action. When young, 
they are white, but afterwards become brownish ; when ma- 
ture, deep brown. 
They have transverse rows of minute hooks; the narrower 
rows are on the posterior part of each segment, and the hooks 
point backward ; those of the wider rows, point forward. These 
Figure 22.—The Bot-fly of Cattle (Zypoderma bovis Latreille), considerably en- 
larged. 
Figure 23.—The full grown larva, enlarged. Both from Packard’s Guide. 
Digitized by Microsoft® 
