438 



ARACHNID A 



di Each spiracle in a stiginal plate (Fig. 700, C) near the fourth pair of legs, 

 t'l Stignial plate in front of fourth leg. 



/i Not on birds (except the genus Dcrmanyasus) 7. Gamasidae 



/a Parasitic on birds 8. Argasidae 



C2 Stigmal plate behind fourth leg 9. Ixodidae 



^2 Spiracles not in stigmal plates, but at the base of the mandibles or near 

 the fourth pair of legs. 

 Ci Aquatic mites. 



fi Fresh-water mites 10. Hydrachnidae 



/a Salt-water mites 11. Halacaridae 



€2 Not aquatic. 



/i Mandibles long and snout-like 12. Bdellidae 



/a Mandibles not so ; body often red. 



i7i Mandibles chelate ; eyes stalked 13. Trombidiidae 



p. Mandibles piercing ; eyes sessile. 

 hi Mid-dorsal line present; not web-spinning. . . .14. Rhyncholophidae 

 hz No mid-dorsal line ; web-spinning 15. Tetranychidae 



Family 1. EEIOPHYIDAE.* (Phytoptidae.) 



Gall mites. Body minute and worm-like, the liinder 

 part being greatly prolonged and ringed ; eyes and tracheae 

 absent ; but 2 pairs of legs present, the hinder 2 parts being 

 represented by wart-like projections or by hairs; pedipalps 

 leg-like and 3- jointed, and holding between them the ros- 

 trum, in which lie the needle-like mandibles; anus at the 

 hinder end. The animals feed on plant juices and are the 

 cause of galls, fuzzy spots, and other deformed structures 

 on plants. The gall always has an opening (differing in 

 this respect from those of the Hymenoptera and the Dip- 

 tera, but not the Homoptera) and vary much in form 

 among the different species. A fuzzy spot or erineum is a 

 dense mass of twisted hairs, among which the mites live. 

 Some of these mites live in buds and kill them, others cause 

 the edge or surface of a leaf to curl or fold, while still 

 others produce abnormal growths on twigs. The family 

 contains about 227 species, 27 species being American. 

 EruinJuf^s Eriophyes von Siebold {Phytoptus Dujardin). 



(Bank^s) Number of rings about the same on upper and under sides 



of the body: about 144 species, 22 American. 

 E. pyri (Pagenstecker). Pear-leaf blister. Length .19 mm.; width 



.05 mm. : causes round, red spots on pear leaves, the opening being on 



the under side; the animals winter in the leaf buds. 



* See "The Phytopti and Other Injurious Plant Mites," by H. Garman, Twelfth 

 Rep. of St. Ent. Illinois, 1883, p. 2.3. "Eriophyidae," by A. Nalepa, Das Tierreich, 

 1898. "Galls and Insects Producing Them," by M. S. Cook, Ohio Nat., Vol. 2, p. 263 : 

 "Vol. 3, p. 419 ; and Vol. 4, p. 125, 1902-04. "The Eriophyidae, Part I, The Apple and 

 Pear Mites," by P. J. Parrott, H. E. Hodgkins and W. J. Schoener, Bull. 283, N. Y. 

 Ag. Ex. St., 1906. 



