NO 1382. THE ACARINA OR MITES— BANKS. 11 



4. Body usually coriaceous, with few hairs; with a specialized seta arising from a 



l)ore near each jiosterior corner of the cephalothorax; no eyes; moutli-parts 

 and palpi very small; ventral openings of alidomen large; never pai'asitic; 



tarsi never with a sucker ORIBATOIDE A 



Body softer, without such specialized seta 5 



5. Living in water HYDRACHNOIDEA 



Not living in water 6 



6. Palpi small, three-jointeil, adhering for some distance to the lip; ventral suckers 



at genital opening or near anal opening usually present; no eyes; tarsi often 

 end in suckers; beneatli the skin on the venter are seen rod-like epimera that 

 support the legs; body often entire; adult frequently parasitic. 



SARCOPTOIDEA 



Palpi usually of four or five joints, free; rarely with ventral suckers near genital 



or anal openings; eyes often present; tarsi never end in suckers; body usually 



divided into cephalothorax and abdomen; rod-like epimera rarely visible; 



adults rarely parasitic 7 



7. J^ast joint of palpi never forms a "thumb" to tlie preceding joint; palpi simple, 



or rarely formed to hold prey; body with but few Jiairs , ..EUPODOIDEA 



Last joint <tf palpi forms a thumb to the preceding, which en<ls in a claw (a few 

 excejitions) ; body often with many hairs TR(_)MBID0IDf2A 



SYNOPSIS OF FAMILIES. 

 DEMODR'OIDEA. 



AVith Imt four legs, of five joints each; living on plants, often in galls. .ERiopnvin.T': 

 With eight legs, of three joints each; living in skin of mammals. Demodicid.'e 



8ARC0PT0IDEA. 



1. With trachefo; no ventral suckers; legs ending in claws; l)ody divided into cephalo- 



thorax and abdomen; the female with a clavate hair between legs I and J I — 



not parasitic on birds or mammals Tarsonemid.e 



Without trachere; no such clavate hair 2 



2. Genital suckers usually present; not parasitic on birds or mammals; skin usually 



without fine parallel lines 3 



Genital suckers absent; parasitic on liirds or mammals; skin with tine parallel 

 lines 4 



3. Legs short, without clavate hair on tarsi I and 1 1 ; living on insects. .Canestrinid.e 

 Legs longer, with clavate hair on tarsi I and 11; not parasitic (except on bees) 



TVROGLYPHID.E 



4. Possessing some specially developed ai)paratus for clinging to hairs of mammals 



LiSTROPHORID.E 



Without such apparatus 5 



5. Living on the plumage of birds Analgesid.e 



Not on plumage of birds, but in living tissues 6 



6. Vulva longitudinal; in skin and cellular tissue of liirds Cytoleichid.e 



Vulva transverse; in skin of mammals and Vjirds Sarcoptid.e 



GAMASOIDEA. 



1 . Parasitic on vertebrates; mandi1)les fitted for piercing; body sometimes constricted 



Dermanvssid.e 

 Free, or attached to insects, rarely on vertebrates, never on birds 2 



2. First pair ot legs inserted witliin the same body-opening as the oral tube; genital 



apertures surrounded l)y the sternum Uropodid.e 



First pair ot legs inserted at one side of the mouth-opening; male genital aperture 

 usually on the anterior margin of sternal plate Gamasid.e 



