Adults superficially resemble honey bees and are similar to slightly larger in size.
Females hover and dart near favored oviposition sites on the host, their abdomens somewhat elongate and curled under. Larvae are grublike maggots with rows of heavy spines at the front border of each segment. Larvae are seldom seen except on autopsy or in horse manure when they mature or after application of a boticide to the host. Common horse bots occur throughout the U. S., nasal bots occur mostly north of Kansas, and throat bots are more prevalent in the Rocky Mountains and western Texas. Larger larvae consume tissue of the horse's stomach or gut lining as well as taking nutrients from the contents.