THE DIGESTIVE ORGANS 153 



surgeon, gave a splendid account of the life-history of the CEstrus 

 equii, or horse bot, which differs very little from what is known 

 to-day. The perfect female insect resembles, both in size and colour, 

 the humble-bee, with the exception that it has only two wings instead 

 of four; it is provided with an egg-laying tube (ovipositor), which is 

 carried under the body in a curved position, and about July or 

 August, when the horses are working or grazing in the fields, the 

 female insect is buzzing about the animals, and depositing its eggs 

 on the shoulders and fore-legs, but more particularly behind the 

 knee-joints, where the eggs — tiny yellow bodies — are seen sticking 

 tenaciously to the hairs in clusters. The eggs when first dropped 

 are covered with a gelatinous material, which glues them to the par- 

 ticular hair on which they are deposited. By the heat of the body of the 

 horse combined with the rays of the sun these tiny eggs are hatched, 

 causing an itching sensation at the roots of the hairs on which they 

 are fixed, and in consequence of this the horse licks the parts with 

 his tongue, when the newly-hatched embryos are carried by the 

 tongue into the mouth, from whence they readily pass along the 

 gullet to the stomach, and with their two little hook-like processes 

 (tentacles) attach themselves to the cuticular or non-sensitive lining 

 on the left or cardiac side of the stomach, where they remain from 

 about July or August until the following May or June. The stomach 

 of the horse is their natural habitat or winter-quarters for their 

 development and growth during the larval stage. When spring 

 comes again, they loosen their hold, pass away with the faeces, and fall 

 upon the ground, when they turn into chrysalides, or the third stage, 

 which occupies about four or five weeks, and in due course of time 

 form the perfect fly (CEstrus equii), ready to perform another circular 

 tour. A large number and variety of medicines have from time to 

 time been tried, yet there is no real known remedy for bots. They 

 seldom cause the death of a horse, as nature thickens the coats of that 

 part of the stomach to which they are attached, so that they cannot 

 get through. Sometimes, however, after leaving the stomach, and 

 in their passage through the intestines, they attach themselves to 

 the lining membrane, and set up irritation and inflammation of the 

 bowels, and cause the death of the horse. When present in large 



