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Give that bot fly some credit. She's no slacker. In fact, she can travel several miles in the quest for a host upon which to lay her eggs, and that host is your horse.
Trouble is, how do you know it's a bot fly? She may be doing a good imitation, but that hairy black-and-yellow insect buzzing around your horse's front legs is not a bee. It's a female horse bot fly, intent on "gluing" her eggs to the most advantageous spots.
Life cycle
There are three species of horse bots, and despite having similar life styles, the females deposit their eggs in different locations on the horse. The most common is Gasterophilus intestinalis, which attaches her eggs primarily to hairs on the horse's front legs and sometimes on the flanks and mane. Gasterophilus nasalis places her eggs on hairs beneath the horse's jaws, while Gasterophilus haemorrhoidalis attaches her eggs to hairs found on the horse's lips.
An adult female bot fly may only live for a week to 10 days, but during that brief lifespan, she can deposit anywhere from 150 to 1,000 eggs. You'll find these yellowish, cream-colored flecks at the ends of the hairs on specific places on your horse, typically around August and September.
The bot's ultimate goal is for those eggs to reach your horse's gastrointestinal tract so the life cycle can continue. In order to accomplish this, they must first hatch into larvae, which either crawl to the horse's mouth, or are ingested when the horse licks or bites at its body where the eggs are attached.
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