Equid-parasite
Guides
Gasterophilinae
stomach bot flies
Gasterophilinae is a subfamily of Oestridae containing large, parasitic flies whose larvae develop in the digestive tracts of herbivorous mammals. The group includes three genera with distinct host specializations: Gasterophilus (equids including horses, zebras, and donkeys), Gyrostigma (rhinoceroses), and Cobboldia (elephants). Adults are short-lived, non-feeding, and exhibit specialized oviposition behaviors. Larvae are obligate parasites that complete development in the host alimentary tract, causing veterinary significance. The subfamily has achieved near-cosmopolitan distribution through association with domestic horses.
Gasterophilus intestinalis
Horse Bot Fly, Horse Botfly
A parasitic bot fly found worldwide that infests the gastrointestinal tract of equids. Adults are bumblebee mimics active in summer, lacking functional mouthparts and living only a few weeks. Females cement eggs to horse hairs; larvae develop in the mouth and stomach for 8–10 months before exiting in feces to pupate. Infestations rarely cause clinical disease but adults are a nuisance to horses.