Horn fly, Haematobia irritans (Linnaeus) (Diptera: Muscidae), adults. Photo by Drees.
Common Name: Horn fly
Scientific Name: Haematobia irritans (Linnaeus)
Order: Diptera
Description: Adults are about half the size of houseflies (about 3/16 inch long) and are gray-black. Part of the mouthparts (proboscis or labium) are long and slender, projecting forward from the bottom of the head along with a pair of structures (palpi) which are almost as long. Immature stages are maggots similar to housefly maggots, distinguishable by the structure of the breathing pores (spiracles) on the back of the body.
The stable fly, Stomoxys calcitrans (Linnaeus) (Diptera: Muscidae), is similar to, but larger than, the horn fly. Its appearance resembles a housefly, Musca domestica, except that on closer examination, it bears a bayonet-like proboscis for piercing and sucking blood as does the horn fly. Larvae develop in manure and decaying vegetable debris (hay, straw and feed) in and around livestock barns along with houseflies. Maggots can be distinguished from house fly maggots by the breathing pores (spiracles) at the back end of the body, i.e., stable fly spiracle plates are triangular while those of house flies are more oval.
Development from egg to adult can occur in 33 to 36 days. Male and female stable flies occur around these areas but also away from livestock areas and in dwellings, biting humans and pets. They can transmit certain animal diseases.
Life Cycle: Females lay eggs singly or in small clusters on the bottom edges of freshly passed cow manure. Maggots hatch in 2-3 days and develop for 8 to 10 days before crawling to a drier area to form a puparium. Adults emerge in 6 to 8 days. Rate of development is slowed in cooler temperatures. Overwintering occurs in a true diapause state in the pupal stage. Populations are most severe in spring and early fall.
Habitat and Food Source(s): Piercing-sucking mouthparts in the adults. A structure (the labella), modified for rasping, occurs at the tip of the proboscis or labium. This part of the mouthpart is thrust into the host and blood is sucked up through other mouthparts (labrum-epipharynx and hypo-pharynx) that lie in a groove along the labium.
Maggots are similar to house flies, having a single mouth hook. Horn flies are attracted to cattle where they rest day during daylight hours. At night flies may leave the animal and rest in barns or on plants. When on the animal they rest on the back, sides, and belly, usually with their heads pointed downwards. Some animals can harbor thousands of flies at one time. Annoyance to cattle caused reduced food consumption, thereby reducing weight gain and milk production. Larvae can be found in cattle manure.
Pest Status: Flies build up in high numbers on cattle.
For additional information, contact your local Texas A&M AgriLife Extension Service agent or search for other state Extension offices.
Literature: Hoelscher, et al. 1993; James & Harwood 1969; Peterson 1960.