Horse bot flies are large, hairy insects that belong to the family Gasterophilidae. They are known for their distinctive yellow or black bodies and can grow up to 2.5 centimeters long. These flies lay their eggs on the legs and bellies of horses, and when the eggs hatch, the larvae burrow into the horse's skin. The larvae develop inside the horse's stomach and intestines, where they can cause irritation and discomfort. After several months, they are expelled from the horse's body and pupate in the ground, eventually emerging as adult flies to continue their life cycle.