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, Erio'phyes 

 {Phyi^toptus) with about one hundred 

 and fifty known species, 3Tonochetus 

 with a single species, and Plvyllocoftes, 

 with about fifty species. 



Among the best known examples 

 are Eriopliyes tiliae, which produces 

 the " nail-galls " on lime-leaves, and 

 E. rihis, the " black - currant Gall- 

 mite," which feeds between the folded 

 leaves of the leaf-buds, and gives rise 

 to swelling and distortion. 



Fam. 2. Demodicidae. — The 

 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 is transversely striated. About ten species have 

 been described, but of these five are probably varieties of 

 D. folliculorum (Fig. 240, A), which infests Man. 



Fig. 240. — Vermiform Mites, highly 

 maguitied. A, iJemodex/oUicu- 

 loruvi ; B, Eriopliyes [Phyptop- 

 tus) rihis. 



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 are very 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 2 H 



