BREEZE-FLIES. 27 



to be nibbled by the horse : the inside of the knee is 

 frequently chosen, but all naturalists must have remarked 

 how commonly the eggs of the bot are deposited on that 

 part of a horse's shoulder which he can never reach with 

 his mouth, and thus, to a casual observer, it would seem 

 that they must perish, and fail in the object for which their 

 parent designed them. Now there is a provision of nature 

 which exactly counteracts this difficulty. When horses 

 are together in a pasture, and one of 

 them feels an irritation on any part 

 of the neck or shoulder which he 

 cannot reach with his mouth, he will 

 nibble another horse in the corre- 

 sponding part of his neck or shoul- 

 der, and the horse so nibbled will immediately perform the 

 kind office required, and begin nibbling away in the part 

 indicated. The horses, when they become used to this fly, 

 and find it does them no injury by sucking their blood, 

 hardly regard it, and do not appear at all aware of its object. 

 When the eggs have remained on the hairs four or five 

 days they become mature, after which time the slightest 

 application of warmth and moisture is sufficient to bring 

 forth in an instant the latent larva. At this time, if the 

 lips or tongue of the horse touch the egg, its operculum 

 is thrown open and the young larva liberated : this readily 

 adheres to the moist surface of the tongue, and is from 

 thence conveyed with the food to the stomach. It is wor- 

 thy of remark, that it is probable the greater part of the 

 eggs deposited by this fly are taken up in consequence of 

 the irritation of other flies, as the Tabani and Stomoxides, 

 which, by perpetually settling on the skin, occasion a horse 

 to nibble himself in those parts, and thus receive the larvae 

 on the tongue and lips whence they are introduced into the 

 stomach. The egg is glued on the hair with the broad end 



