Gastrophilus sp.

A first stage larva is observed in the gingiva (arrow). Prof. Kenjiro Kikuchi clarified this growth cycle.

Horsefly larvae in the gastric mucosa
Second stage larvae live in the stomach for 10 months, and third stage larvae leave the stomach and live again in the rectum. The larvae are excreted together with stools, become chrysalises in the soil, and emerge as adults after about a month. Eggs are laid in the hair in the fore limbs, licked by horses, and enter the mouth.

Growth cycle of horse bot flies (Figure in another paper) Egg laying in the hair Gingiva Larvae live in the gingiva, undergo the first molting, and descend into the stomach Larvae remain in the stomach for about 10 months. The free-living period is not long.

Masanobu Goryo
Address inquiries to the following.
Department of Veterinary Pathology, Faculty of Agriculture, Iwate University., Morioka, 020-8550, Japan