31 
This species was more particularly known to Reaumur and 
Vallisneri, and is the same about which Gaspari was led to pro¬ 
pagate his wonderful accounts of the Fly actually entering the 
body of the animal to deposit its eggs, a thing on several ac¬ 
counts impossible ; for, in the first place, it is to be lemaikcd, 
that no animal of this description is so unwise as to commit an 
act of severe and deliberate punishment upon itself, and of self- 
destruction, for all its members must have been broken by passing 
the strong sphincter of the Horse’s rectum ; or if the rectum 
was first protruded, and, as they pretended, entering at this 
moment, he became enclosed among its folds, he would be so 
unfavourably situated, being surrounded with slime, wetted, and 
compressed by the intestine and its contents, he could not cer¬ 
tainly perform with the requisite deliberation this important act: 
but the anus is in fact closed, rather than opened, by any irrita¬ 
tion externally applied. The Fly would be crushed in attempting 
to pass the sphincter of a horse’s rectum ; and having no means 
of holding while depositing its eggs, it would be quickly evacu¬ 
ated with the dung ; and it is evident that the whole of the ova, 
to the amount of two or three hundred, must be deposited in 
one horse, as it is impossible, if the Fly survived, that it could 
undergo this punishment a second time, for the heat and mois¬ 
ture of the rectum would at least destroy its wings, and prevent 
it from attaining this situation. 
I mention these objections, not as merely relating to this spe¬ 
cies but that it may not be credited of the GE. Nasa/is, or indeed 
of any of them, that they really enter the body of the animal to 
obtain for their young a situation there. 
* The fly Dr. Gaspari saw was without doubt the Hippobosca Equina , or Forest 
Fly from the circumstance of its getting beneath the tail, which this Fly often does, 
and all the rest of the account was added from imagination. That a fly nsight 
deposit its eggs on the verge of the anus, is not impossible; but we know of no 
example or instance of it at present. 
