THE WATER-MITES (HYDRACARINA) 



865 



29 (28) Genital cleft flanked by two large movable valves, and also ace- 

 tabula set free in the body surface. Koemkea Woicott 1900. 



A beautiful mite of striking form, 

 being greatly compressed and actually 

 concave dorsally; with swimming- 

 hairs. Brightly and variously colored. 

 One widely-distributed species, K. 

 concava Woicott, adapting itself to 

 varied conditions, and often common. 

 Of small size measuring 0.6 to 0.7 mm. 

 in length. 



Fig. 1334. Koemkea concava Woicott. 

 Epimeral field and genital area, male. X 65. 

 Inner side, palpus, male. X 278. Side view, 

 capitulum and rostrum female. X 277. 

 (After Woicott.) 



30 (27) 



31 (36) 



32 (35) 



33 (34) 



Rostrum short 31 



Suture between the dorsal and ventral plates continuous, completely 



enclosing the dorsal plate, or open posteriorly 32 



Acetabula lying near the genital cleft, no modification of leg IV in 



the male. 



33 



Ep. IV quadrilateral in form Mideopsis Neuman 1880. 



A mite of bright colors, with body almost circular 

 in outline, slightly concave dorsally; a short rostrum; 

 swimming-hairs; 3 acetabula on each side, outside of 

 which are narrow, sickle-shaped flaps. One species, 

 M. orbicularis (Miiller), common to Europe and 

 America and widely distributed in this country. Of 

 medium size averaging about i mm. in length. 



Fig. 1335. Mideopsis orbicularis {M.\i\\er). Ventral sur- 

 face, female. X 23. Outer side, right palpus. X 123. 

 (Modified from Piersig.J 



34 (33) Ep. IV triangular Xystonotus Woicott 1900. 



Body elliptical; capitulum small and 

 camerostom slightly developed into a 

 rostrum; no swimming-hairs; 3 acetabula on 

 each side, flanked by movable flaps. The 

 genus containing a single species. A', asper 

 Woicott, known only from two female 

 specimens from Michigan. Of small size, 

 0.61 mm. long. 



Fig. 1336. Xystonotus asper Woicott. Ven- 

 tral surface, female. X 43- Outer side right 

 palpus. X 195. (After Woicott.) 



