INSECTS MOLESTING FARM ANIMALS 277 
Horse-flies (Family Tabanidae) develop in moist soil or 
mud, usually in the beds of reedy brooks and ponds. One 
finds the larvae (fig. 77) among the roots of aquatic weeds 
and grasses by lifting these from the water. The annual 
crop of flies matures in midsummer. The males sip nectar 
and plant juices, and are short-lived; the females bite 
fiercely and suck the blood of all the larger hoofed mammals. 
They are troublesome only by day. When fully mature 
they lay their eggs on the vertical stems and leaves of aquatic 
plants, just above the surface of the water. Many handsome 
flies (see fig. 118) are found in this group. 
The bot-flies (Family Oestridae) are parasitic 
as larvae. Three are notable and dangerous: 
one in the alimentary tract of the horse, 
causing various derangements; one in the 
ee frontal sinus of the sheep, causing vertigo to 
Fre 19 cee the animal and often killing it; one under the 
Siete ac skin on the backs of cattle, causing great lumps 
Comstock, from 
Com cisck + that may be readily felt by running one’s hands 
Barual for tke over an animal’s back. These larvae (known 
SEE as ‘‘ox-warbles”’) are the easiest of the bots to 
observe. Over each of them is a hole in theskin, out of which 
the larva will emerge when grown. When approaching the 
time of emergence (best in the spring) it may be brought to 
light prematurely. By placing one’s thumbs at either side 
of the lump and pressing hard, the warble may be made to 
pop out through the hole into the daylight. 
The horse bot-fly is most easily observed of the adult 
insects. It often follows teams along the highways or about 
the fields, and its presence may be suspected from the 
frenzied action of the horses, flinging their heads upward. 
The bot-fly does not bite; it merely seeks to attach its eggs 
to the hairs about the front legs and shoulders of the horse, 
within reach of his mouth. But the horse instinctively 
