OESTRUS. 3()5 
found in similar situations in Deer and some other 
quadrupeds. It is a smaller species than either of 
the two preceding, and is of a whitish-grey co- 
lour, with the thorax marked by four longitudinal 
black streaks, and the abdomen speckled with 
black. The larvm are nearly as large as those of 
the Oestrus Equi, and, according to the observa- 
tions of Mr. Clark, are of a delicate white colour, 
flat on the under side, and convex on the upper; 
having no spines at the divisions of the segments, 
though they are provided wdth tentacula at the 
small end. The other is truncated, with a promi- 
nent ring or margin. When young these larvae 
are perfectly white and transparent, but as they 
increase in size the upper side becomes marked 
with two transverse brown lines on each segment, 
and some spots are seen on the sides. They 
move with considerable quickness; holding with 
their tentacula as a fixed point, and drawing up 
the body towards them. Mr. Clark in his descrip- 
tion of this species observes that he has mostly 
found the laryae in the horns and frontal sinuses of 
Sheep, and remarks that the membranes lining 
these cavities were hardly at all inflamed, Avhile 
those of the maxillary sinuses were highly so. 
From this circumstance he is led to suspect that 
they inhabit the maxillary sinuses, and crawl, on 
the death of the animal, into these situations in 
the horns and frontal sinuses. When full-grown 
they fall through the nostrils, and change to the 
pupa or chrysalis state, lying on the ground, or 
adhering to some, blade of grass. The fly pro- 
