Acarina 271 



pp. Hind part of the male abdomen without 

 lobes. Live in ears of dogs and cats 

 .................. Olodectes Canestr. 



0. cynotis Hering (fig. 150 e) has been 



taken in the United States. 



i. Palpi usually of four or five .segments, 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. 



f. Last segment of the palpi never forms a thumb to the preceding 

 segment; palpi simple, or rarely formed to hold prey; body 

 with but few hairs ................... ..... EUPODOIDEA. 



g. Palpi often geniculate, or else fitted for grasping prey; mandi- 

 bles large and snout like; cephalothorax with four long 

 bristles above, two in front, two behind; last segment of leg I 

 longer than the preceding segment, often twice as long ..... 



.......................................... BDELLID^E. 



gg. Palpi never geniculate (fig. I58a), nor fitted for grasping prey: 

 beak small; cephalothorax with bristles in different arrange- 

 ment; last segment of leg I shorter or but little longer than 

 the preceding joint; eyes when present near posterior 

 border .................................... EUPODIDJ2 



Moniez has described a species from Belgium (Tydeus 

 molestus) which attacks man. It is rose colored; eye- 

 less; its legs are scarcely as long as its body, the hind 

 femur is not thickened; the mandibles are small and the 

 anal opening is on the venter. The female attains a 

 length of about 0.3 mm. 



ff . Last segment of the palpus forms a thumb to the preceding, which 

 ends in a claw (with few exceptions) ; body often with many 

 hairs (fig. 158 k) ..................... /TROMBIDOIDEA. 



g. Legs I and II with processes bearing spines; skin with several 

 shields; coxae contiguous ...................... CECULID^E. 



gg. Legs I and II without such processes; few if any shields. 



h. Palpi much thickened on the base, moving laterally, last 



joint often with two pectinate bristles; no eyes; legs I 



ending in several long hairs; adult sometimes parasitic 



........................................ CHEYLETID^E 



Cheyletus eruditus, which frequents old books, has once 

 been found in pus discharged from the ear of man. 

 hh. Palpi less thickened, moving vertically; eyes usually present; 



leg I not ending in long hairs. 



i. Coxae contiguous, radiate; legs slender, bristly; body with 

 few hairs; no dorsal groove; tarsi not swollen .......... 



ii. Coxae more or less in two groups; legs less bristly. 



