Horse Bots Traditionally, the most effective treatments for the control of horse bots have been applied at least 30 days after the first killing frost. Bots, not true worms, are the larval stage of bot flies.
Bot flies are active from midsummer until the first killing frost.
Adult bot flies, resembling honey bees in appearance, may cause animals to instinctively fear them. Females, unable to feed or bite, lay 150 to 300 eggs in a life span of 7 to 10 days. Eggs accumulate until adults are killed by frost and can remain viable for several months. Eggs incubate in 1 to 2 weeks and hatch only if licked or eaten. Also, clipping hairs infested with bot eggs will aid in control.