and lying apparently in a torpid state, though in the middle of 
summer. 
To prevent unnecessary repetition, these Flies are described 
with the other species, both in English and Latin, at the conclu¬ 
sion of this Essay. 
On the Oestrus Hjemorrhoidalis, or Fundament Bot. 
I shall begin my account of this species at the same point as 
the former, with the deposition of the egg, the manner of which, 
I appiehend, has never been described or known before. 
This proceeding I have frequently witnessed, and it may be 
seen by any one desirous of observing so curious a fact upon most 
of the commons of this country. About Ditton, Molesey, and 
Esher, I have more particularly seen it where the cattle are 
much annoyed with it ; and I once also saw this same operation 
in the fertile meadows of Holland, near to Groningen, while be¬ 
ing conducted a prisoner through this country to Amsterdam, and 
I have caught the Fly more than once in the very act in my 
hands.—See fig. 17 . PL I„ 
The part chosen by this Insect for this purpose is the lips of 
the Horse, which is very distressing to the animal from the exces¬ 
sive titillation it occasions ; for he immediately after rubs his 
mouth against the ground, his fore-legs, or sometimes against a 
tree, with great emotion ; till the animal at length finding this 
mode of defence insufficient, enraged he quits the spot, and 
endeavours to avoid it by galloping away to a distant part of the 
field ; and it the Fly still continues to follow and tease him, his 
last resource is in the water, where the Oestrus never is observed 
to pursue him. These flies appear sometimes to hide themselves 
in the grass ; and as the horse stoops to graze they dart on the 
mouth or lips, and are always observed to poise themselves dur- 
11 
mmmmm 
—I 
