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.
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.