37 
a margin round to prevent the escape of the Larva on its falling 
from the intestines ; or indeed, and which would be better, a 
small apartment entirely constructed for this purpose, of dimen¬ 
sions that would give the horse his liberty, and where he is 
intended to be chiefly kept during the two or three months of 
summer. On this floor might the Larvre, by examining the dung 
two or three times a day, be collected, and thus fully grown 
Larvas being obtained, there would be no difficulty in raising them 
to the state of a Fly by keeping them in boxes filled with earth, 
or a mixture of dung and earth, till the Fly appeared. In this 
way what is unknown of their sexes, species, and history, might 
be correctly made out, and further on the Fly coming forth, 
if confined in a suitable apartment, they might even be presented 
to the Horse, and the mode of depositing their eggs be seen, 
their copulation having been first permitted, which Vallisneri 
informs us they are not shy in performing coram teste. 
I am induced to notice in this place a Fly belonging to this 
genus, a figure of which is given at No. 28, and whose history wd 
are at present quite unacquainted with. I obtained it, with some 
other Insects in the sale of Drury’s collection, about ten years 
ago, and by way of distinguishing it till its history becomes known, 
shall bestow on it the name of Oestrus Microcephalus. It may be 
the Oe. Trompe or Pecorum of Fabricius, or both.—See the 
description at the conclusion of this essay. Its general appear¬ 
ance, and the distribution of the tendons of the wing, would lead 
me to refer it to the Cuticular Oestri. 
Another species also, whose history we are at present in the 
dark about, is given at No. 30, which I formerly placed under 
HcemorrhoidaUs as a variety (S, but observed that it differed from 
it in the essential circumstance of having a large white wing- 
scale : ft variat squama halterum major! lactea magna ac facie 
magis depressa. Lin. Soc. Trans. Vol. III. p. 328. It has since 
been taken on the heaths near Plymouth by Dr. Leach, who has 
K 
