HIPPOJ80SCA. 
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of a dull green colour: it is often observed on the 
bodies of various birds, which it infests in a very 
troublesome degree. 
^ Hippohosca Hirundims is equal in si^e to the 
H. avicularia, and is of a livid greenish colour, 
with the abdomen deeply emarginated behind, so 
as to represent the usual figure of an inverted 
heart: the wings are of a sharpened or lanceolate 
form; and the feet, instead of being terminated 
by two claws only, as in the generality of insects, 
have six sharp, curved divisions; and though four 
of these may rather be considered as a kind of 
spurious claws, yet they still operate as so many 
real unguiculi, and enable it to adhere with great 
tenacity*: This species is very often observed on 
the bodies of Swallows, Swifts, and Martins; and 
may almost always be found in their nests. Its 
motion, like that of the two preceding kinds, is 
brisk, but irregular, moving in all directions with 
equal facility. The egg or pupa of this species is 
at least as large in proportion to the parent as 
that of the Horse-Fly: it gradually changes to a 
jet-black colour, and the complete Fly is usually 
produced from it in the space of a month. 
Hippohoaca ovina is commonly known by the 
name of the Sheep-Tick, and is very frequently 
found imbedded in the wool of those animals. It 
is of a reddish-brown colour, and differs from the 
rest of the genus in being entirely destitute of 
wings. Its pupa is also of a reddish-brown co- 
lour, exactly oval, and of a shining surface. 
