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 f Gastrus 
EquijJ 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 ; 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 bell}^ ; 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 bursty, 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. 
