32 
On dissection this Larva is found to possess similar air tubes 
and alimentary canal. When it is ripe, and has passed through 
the intestines, its skin becomes of a greenish-red hue. It gene¬ 
rally assumes the Chrysalis state in about two days after leaving 
the rectum, and is then of a deep-red colour.—See fig. 19 . 
The Larva of this species may be obtained from almost any 
Horse that has been much the preceding year at grass, and ex¬ 
posed to these Flies, and will be found during the summer months 
sticking more or less within the verge or opening of the anus, 
adhering to its soft lining, and producing considerable irritation 
and uneasiness. Indeed I once well remember being on a tour 
of pleasure in the Isle of Wight, and experiencing much annoy¬ 
ance from these larvm. The little Horse I had hired for the jour¬ 
ney became so lazy and unwilling to go on, and moved so awk¬ 
wardly, that I could not keep pace with my company, and I was 
at a loss how to proceed ; but on casually taking up the tail, I 
discovered three or four of these Insects hanging to the rectum, 
and their removal instantly proved a cure.* 
When they are taken away from these parts with a view of 
obtaining the Fly from them, it should be done with care, and 
by a light sudden twitch or jerk of the fingers, not compressing 
them ; for if squeezed much in this tender state, (for all Insects 
are very much so when about to change to Chrysalis,) the Fly is 
damaged, if not killed : in which case, though they undergo their 
change to the Chrysalis, it never hatches. 
From the beginning of June to the end of July or August, 
they are found hanging in this way to the end of the rectum, as 
though reluctant to leave their warm habitation. They appear 
never to change their skin during their growth, as many other 
* Vegetius observes, Cossi et lumbrici qud curd tollantur ad manum. Diligenter 
tentabis et invenies vermes collectos exisse in singulis locis et intestinum pertundere 
ex qua necessitate nascitur dolor periculosus. Digitis evelle eos qui quidem vix evel- 
luntur et ipsa tibi in raanu coherent, ut difficile eos projicias. Lib. I. cap. 52, 
