Both kinds are strong fliers. Only the females suck blood, and they are vicious biters. The males feed on nectar and are of no consequence as animal pests. These flies are the most annoying of livestock pests. Although these flies often attack man and can inflict painful bites, humans are not their primary hosts.
Deer flies more commonly attack man than do horse flies.
Black Horse Fly, Tabanus spp. Deer Fly, Chrysops spp. Back To Top Life History Eggs are deposited in masses of up to 1,000 on vegetation growing in or overhanging streams, ponds or swampy areas. Eggs usually hatch in about 4 to 7 days. Larvae quickly drop to the surface of the water or moist soil and quickly burrow into the mud, damp earth or decaying matter.