344 MANUAL OF EQUINE MEDICINE. 



Dr. Manson considers that the eye is not the usual 

 habitat for this parasite. 



The tracks of this worm may be readily seen. 



11. FILARIA SANGUINIS EQUI— These microscopic 

 nematodes were found by Dr. Sonsino in the blood of an 

 Egyptian horse. 



IV. (ESTRIDJE, OR GADFLIES. 



GASTROPHILUS EQUI, or Common Gad-fly, or (Estrus 

 Equi. — Description. — The bot, which is the larval form 

 of the gad-fly, has eleven segments arranged in double 

 rows, and is of a red colour. The head is narrow and 

 pointed, and the mouth is small, and placed between two 

 large hooks or maxillae. Between the hooks are two horny 

 plates, called mandibles. The tail is broad, truncated, and 

 flattened at the end. 



Development. — The gad-fly attacks the animals in late 

 summer to lay its eggs, and this is done by fixing them to 

 the neck, shoulders, and inner part of the fore-leg, espe- 

 cially about the knees, by means of a sticky or glutinous 

 secretion. 



The horse licks these parts with his tongue, and in less 

 than three weeks after being first deposited the larvae 

 escape. 



From the tongue they gain access to the stomach, where 

 they fix on to the mucous membrane by means of their 

 hooks. 



When they attain their full size they become loose, and 

 escape with the faeces and bury themselves in the soil, where 

 they are transformed into pupae. 



Having remained in the earth about six or seven weeks, 

 they emerge from their pupa cocoons perfect dipterous 

 insects. 



