17 
separates those of the Horse from all the other species. The 
next division will be the Cut icola:, or those which live in their 
Larva state beneath the skins of animals ; and the third the Cavi- 
colce, or those living in the cavities of the face. Perhaps a fouitli 
divisionmight be constituted, including those of the Fauces, if the 
accounts we at present entertain of them be true, and the neives 
of the wings of these different families appear also to afford cha¬ 
racters for these divisions, which was first observed to me by my 
friend Dr. Leach. 
The large Horse-bot being the most interesting to us in this 
country, I shall begin my account with that species, and lollow 
it with the other species of that division. 
Of the Oestrus Equi, or Large spotted winged Horse-bot. 
As it is necessary to break into the circle of its history at some 
point, I shall begin with an account of the egg, and its depo¬ 
sition upon the skin of the legs of the horse, which is done in 
the following remarkable manner When the female has been 
impregnated, and the eggs sufficiently matured, she seeks 
among the horses a subject for her purpose, and approaching him 
on the wing, she carries her body nearly upright in the air, and 
her tail, which is lengthened for the purpose, curved inwards and 
upwards : in this way she approaches the part where she designs 
to deposit the egg ; and suspending herself for a few seconds 
before it, suddenly darts upon it, and leaves the egg adhering to 
the hair: she hardly appears to settle, but merely touches the 
hair with the egg held out on the projected point of the abdomen. 
The egg is made to adhere by means of a glutinous liquor se¬ 
creted with it. She then leaves the horse at a small distance, 
and prepares a second egg, and, poising herself before the part, 
deposits it in the same way. The liquor dries, and the egg e- 
E 
