Gasterophilus intestinalis – Horse Bot Fly
Female adult bot flies glue their eggs to the hair on the fore legs of horses. The horse
licks the eggs while scratching and the heat of the tongue causes the eggs to rapidly hatch
and the larvae to attach to the inside of the mouth. The larvae then travel down the
esophagus to the stomach where they attach to the stomach wall. They feed on the
horse’s food for the next 7-9 months before dropping off and traveling through the rest of
the gastrointestinal tract. They pupate in manure and emerge as adults. Larvae have
rows of heavy spines that may cause irritation to the mouth or stomach and secondary
infection may result.