XVIII VERMIFORMIA—-ASTIGMATA 465 
guarded with hairs, and the Mites live gregariously within it, 
apparently feeding upon the hairs which grow abundantly on its 
inner surface. In Insect-galls each 
insect larva lives in a separate closed 
chamber. 
The Eriophyidae are unique among 
Mites in possessing only two pairs of 
legs, situated quite at the anterior 
part of the body. The mouth-parts 
are very simple. 
There are three genera, Hriophyes 
(Phyptoptus) with about one hundred 
and fifty known species, J/onochetus 
with a single species, and Phyllocoptes 
with about fifty species. 
Among the best known examples 
are Hriophyes tiliae, which produces 
the “nail-galls” on lime-leaves, and 
E. ribis, the “black-currant Gall- 
mite,’ which feeds between the folded 
leaves of the leaf-buds, and gives rise MT Nm on Mies: gly 
> D5 magnified. A, Demodea follicu- 
to swelling and distortion. Hee Eriophyes (Phyptop- 
Fam. 2. Demodicidae. — The igri tm 
single genus Demodex which constitutes this family consists of a 
few species of microscopic Mites which inhabit the hair-follicles 
of mammals, and are the cause of what is known as “ follicular 
mange,” some other forms of mange being due to members of the 
succeeding family. Demodex possesses eight short, three-jointed 
legs, each terminated by two claws. The abdomen is much 
produced, and js transversely striated. About ten species have 
been described, but of these five are probably varieties of 
D. folliculorum (Fig. 240, A), which infests Man. 
Sub-Order 2. Astigmata. 
The Astigmata are Mites of more or less globular form, with 
chelate chelicerae and five-jointed legs. All members of the group 
are eyeless. Their habits arevery various, some feeding on vegetable 
matter and others on carrion, while a large number are parasitic 
on animals. Tracheae are absent. There is only one family. 
VOL. IV 2H 
