THE ACAEIXA OR MITES. 49 



I 12. Epimera of both sexes united into one plate 13 



Epimera (at least of female) not united into one plate 18 



13. Fourth joint of palpus with a projection below Xystonotus. 



Fourth joint of palpus without projection 14 



14. Dorsum without a bowed furrow 15 



Doi-sum ^^^.th a bowed furrow 16 



15. Hind tarsi without claws Oxus. 



Hind tarsi with claws Lebert ia. 



16. Bowed furrow open in front, ends extending over on venter Axonopsis. 



Bowed furrow not open in front 17 



17. Second joint of palpus \vith a projection below; genital aperture at tip of 



body Aturus. 



Second joint of palpus without projection; genital aperture much before 



tip of body Mideopsis. 



18. Fourth tarsus without claws; a long bristle at tip Limnesia. 



Fourth tarsus with claw as with others 19 



19. Genital opening with lip each side nearly covering the disks; palpi Avith 



spine below on joint 2 Sperchon. 



Disks near genital opening fully exposed 20 



20. Epimei-a of female in two groups ^ Koenilcea. 



Epimera of female in three groups; genital opening usually with disks each 



side 21 



Epimera of female in four groups 22 



21. Apical joints of leg I normal Hiigrohates. 



Fifth and sixth joints of leg I curved Atractides. 



22. Genital opening with three disks each side 23 



Genital opening with more than three disks each side 25 



23. Second joint of palpus with spine beneath TyrreUia. 



Second joint of palpus without spine beneath 24 



24. Legs and palpi extremely long Hydrochoreutes . 



Legs and palpi rather sliort, male with middle joint of hind legs enlarged. ^c^rcws. 



25. Legs I and II with spirally ringed bristles : . Neumania. 



Legs without such bristles 26 



26. Genital opening at tip of body 27 



Genital opening much before the tip 28 



27. Without swimming hairs on legs; fourth joint of palpus without three spurs 



below ; genital area large Feltria. 



With a few ssvimming hairs; fourth joint of palpus with three spurs, or 



papillae, below ; genital area smaller Atax. 



28. Hind epimera ^^ ith a pointed projection below; palpi larger than legl.Najadicola. 

 Hind epimera without a projection; palpi smaller, and ending in two ortln-ee 



small claws; the fourth has two papillae below Fiona. 



29. Median eye in the soft skin Eupatra. 



Median eye on a plate Hydryphantes. 



The immature forms are known in many genera and these may be tabulated as 

 follows: 



1. Coxae united into a large plate each side leaving only a narrow groove be- 



tween them 7 



Coxae not united into a large plate lea\T.ng only a narrow median line; beak 

 large and prominent; palpi of three or four joints usually extended; no 

 dorsal sliields 2 



2. Coxae I and II partly united, palpi curved under beak Eylais. 



Coxae I and II separate, palpi extended 3" 



3. Beak nearly as long and as broad as body; tarsi subtruncate at tips. . .Hydrachna. 

 Beak only about one-half length of body; tarsi tapering to fine point 4 



4. A median pore between eyes 5 



No median pore between eyes 6 



5. Beak divided by median line for entire length Hydryphantes. 



Beak divided only on apical hah Thyas. 



6. Legs with six joints beyond coxae Ltiiniocharcs. 



Legs with apparently but five joints beyond coxae DipJodontus. 



7. Hind legs fully three times as far from second as second from first; hind 



legs with fifth joint from tip several times as long as broad; body usu- 

 ally elongate Limnesia. 



BDind legs but little farther from second than second from the first pair 8 



i 



