THE INSECT WORLD. 



359 



rapidity. This insect derives its common name from the fact 

 that it seems to prefer clustering in great numbers at the base of 



Fig. 416. 



Horn-fly, Hcematobia serrata.—a, egg; b, fly; c and rf, head and mouth parts; all 



enlarged. 



Fig. 417. 



the horns of cattle, although it is really just as abundant on the 

 flanks, upon the udder, and in other places where it cannot be 

 readily reached by the animals. The fly seems to confine its at- 

 tacks to horned cattle, although it has been seen on mules in the 

 State of New Jersey. Like the stable-fly, it 

 is a blood-sucker, and both species are often 

 found on animals at the same time, keeping 

 them in that state of constant irritation 

 which prevents their proper feeding and 

 digesting, and keeps them poor and in no 

 condition to produce a free flow of milk. 

 Not only in the fields or pastures are the 

 cattle annoyed by these insects, but in the 

 stable as well, so that the animals get no 

 rest night or day. Eggs are laid in fresh 

 cow-dung, and before this has an oppor- 

 tunity to dry under ordinary conditions, the 

 larvae are full-grown and ready to pupate. It is the immense 

 number of these insects that makes them dreadful, and when the 



Egg of horn-fly. — i, 

 unhatched, from side; 



2, hatched, from front; 



3, same, from side, to 

 show lid-like structure; 

 all enlarged. 



