799 
No. 175.1 
As this group of insects is so deeply interesting, particularly to the 
farmer, some account of those species which most annoy our domestic 
animals may be given in this place. 
The bot-fly of the horse being regarded as the type on which Lin- 
nasus founded his genus CEstrus, that name is retained for it by the 
latest naturalists, instead of the name Gasterophilus proposed by Dr. 
Leach. The most common species, CEstrus equi, Linn., is from a half to 
three-fourths of an inch long. Several specimens before me exhibit 
considerable differences in the details of their coloring. The thorax or 
middle segment of the body is black, the head and abdomen varied 
with brown, dull yellow and sometimes black, which last is the preva¬ 
lent color of the exserted tip of the female abdomen. The body is cov¬ 
ered with yellow hairs. But the mgst constant character by which to 
distinguish this species is the markings upon its wings, these being 
transparent, with a brown, smoky-like band across the middle and two 
spots of the same color at the tip. The pupa, as it has occurred to my 
notice, is half an inch long and a quarter of an inch broad, nearly oval 
but somewhat smaller anteriorly. It is of a black color, encircled with 
rows of short sharp spines or thorn-like points directed backwards, there 
being one such row upon each segment. On the anterior end are two 
little processes like horns. I have sometimes met with this pupa in the 
dung of the horse, the larva in these instances probably having been 
so far matured towards its pupa state when it was voided from the ani¬ 
mal that it was unable to crawl into the ground as it usually does. 
The CEstrus nasalis, Linn., is the name applied by the latest author¬ 
ities to the species which has been current in books under the name of 
veterinus. This is of nearly the same size with the preceding, and has 
the head yellow, the remainder of the body being black. Hairs orange 
yellow ; those of the abdomen whitish except on the third segment, 
where they are black ; wings, hyaline. This and the preceding are the 
only species of bot-fly that infest the horse, that I have met with in this 
country, though it is not improbable that others exist. There is per¬ 
haps no part of the science of entomology where so great confusion has 
prevailed in the names and descriptions of the species as here, and the 
authorities are so discordant that it is difficult to determine which names 
are to be sanctioned as the correct ones. 
The Hypodcrma Bovis, Linn., or gad fly which produces the war¬ 
bles on the backs of cattle, is of a size corresponding with that of the 
common bot-fly of the horse. It is of a black color and clothed with yel¬ 
lowish-white hairs, except on the third segment of the abdomen, where 
they are biack. The wings have a brownish tinge. 
