22 VETERINARY PARASITOLOGY 
It is a very degenerate parasite, is oviparous, and 
goes through a life-cycle similar to that of the Sar- 
coptide. 
In shape and general appearance, especially when 
viewed under a low power, the parasite much resembles 
a maggot, though when closely observed 
the differences in structure are obvious. 
It is about ;4, inch in length. 
The head is rounded from side to side, 
and is somewhat longer than wide. It 
carries two pairs of jaws, placed one above 
the other. The lower pair, or maxilla, 
act somewhat like a pair of miniature 
tongs, and grasp the substances which 
the upper pair or mandibles masticate. 
In addition, the head bears a pair of 
feelers, which are finely segmented, and 
there is also present a structure known 
as the oral valve. The eyes are two 
in number, and are situated laterally. 
The body consists of a thorax and 
abdomen. The thorax is the widest por- 
tion, and bears four pairs of short three- 
jointed legs. The abdomen is triangular, 
the base being formed at its junction 
Fic.5.—Acarus With the thorax. It shows a dark area 
Demovex For- about its centre, supposed to represent 
TicororuM. viscera. The whole length of the body 
is transversely striated, and the edges 
are correspondingly notched. In the 
hexapod larva and nymph stages the parasite has only 
small tubercles, in three pairs, in the place of legs, and 
the body shows no transverse striation. 
The Demodex inhabits the sebaceous glands of 
the skin, and one gland may contain from only 4 
few up to a hundred or more parasites. The number 
if 
Up ava 
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HM 
Highly magni- 
fied. 
