|File:Horse Botfly Imago.png|
Gastrus Meigen, 1824
Gasterophilus is a genus of parasitic flies in the family Oestridae which includes the horse bot flies. They lay eggs in the fall on the face and around the lips and noses of horses, caribou, donkeys, and similar animals, usually equines. When the eggs hatch, the larvae typically proceed to either the nasal passages or the stomach of the host animal. Those larvae which grow in the stomach are passed in the feces of the host, and they burrow into the soil to pupate. Those that grow in the nasal passages may drop out of the nose to pupate in the ground. It is one of the few insects that produce haemoglobin. Note the pink colour of the larvae. 
There are exceptional cases of human babies infected by these flies.
G. intestinalis eggs on a horse
G. intestinalis eggs on a horse (closer)
G. intestinalis larva
drawing ofG. intestinalis larvae in a horse's stomach
G. intestinalis adult female.
- ↑ Meyer, H.J., R. Dean Christie, Dean K. McBride. Insect Pests of Horses. NDSU Extension bulletin 55. 
- ↑ Royce, L. A., Rossignol, P. A., M. L. Kubitz, AND F. Randell Burton 1999. RECOVERY OF A SECOND INSTAR GASTEROPHILUS LARVA IN A HUMAN INFANT: A CASE REPORT. Am. J. Trop. Med. Hyg., 60(3), 1999, pp. 403–404 
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