MAY. 135 



bers. The female is a kind of dull yellow-olive, a colour 

 which the females of almost all our gaily coloured birds pos- 

 sess : probably to secure them from observation while per- 

 forming their maternal duties. 



C. I picked up a few days ago,, in the horse-stable 

 among the ordure, a somewhat oval larva of a dirty white 

 colour, encircled with rings of minute hooks. It is now be- 

 come a pupa, not by throwing off the skin, but by the inte- 

 gument itself becoming more rigid : it is also a little altered 

 in form, being cylindrical, and its colour is a shining chestnut 

 brown. 



F. It is, no doubt, the Horse Gad-fly, or Bot ( Gastrus 

 Equi,) but it is not likely that you will raise it to the per- 

 fect state, unless you have covered it with damp earth. The 

 Bot-fly deposits its eggs in summer and autumn, on those 

 parts of the horse's body that he can reach with his mouth : 

 a curious provision is made for the deposition of the egg j the 

 oviduct of the female is capable of being thrust out to some 

 length, and is composed of tubes, which slide one within 

 another, like the tubes of a spyglass. When the fly is 

 hovering around a horse, I have often observed this oviduct 

 protruded, and turned up under the belly ; if caught at this 

 time, we find that an egg is already ejected, and lies at the 

 very extremity, ready to be deposited. The slightest con- 

 tact with the hair of the horse effects this, and the egg is left 

 sticking to the hair. We frequently see the fore legs and 

 shoulders of our horses almost white with the numbers of 

 these eggs. In a short time they become ready for hatching, 

 and the least touch of moisture, even a wet finger, will in- 

 stantaneously cause the egg to burst, and the little maggot 

 crawls and writhes about. As the horse frequently licks 

 himself, hundreds of these eggs must be hatched, and the 

 worms adhere to his tongue ; and as many as escape the 

 grinding of his teeth, go down with his food into the stomach. 



