THE WATER-MITES (HYDRACARINA) 

 54 (6i) Posterior margin of ep. IV rounded or transverse . . 



871 

 SS 



55 (58) With swimming-hairs 56 



56 (57) Transverse diameter of ep. IV the greater, suture between epp. 

 Ill and IV complete; no prominent papillae on pal. seg. 4, 

 acetabula very numerous Neumania Lebert 1879. 



Mites of small to medium size, varying 

 in length from 0.5 to i .6 mm., with soft body, 

 tending more or less to develop chitinous 

 plates or beset with chitinous points, rarely 

 smooth; leg IV usually with feathered spines. 

 Brightly colored, red or bluish forms, active, 

 but not markedly voracious. Several North 

 American species, common, and widely dis- 

 tributed. 



Fig. 1347. _ iVcMwoMia spinipes (Muller), a 

 European species represented in this country by a 

 closely allied form. Ventral surface, male. X 40. 

 Outer side, palpus, male. X 70. (Modified from 

 Piersig.) 



57 (56) Longitudinal diameter of ep. IV at least equal to the transverse, 

 suture between epp. Ill and IV incomplete mediaOy; pal. 

 seg. 4 usually with prominent papillae ; s or 6 acetabula on 

 each side on one or two plates. 



(Non-parasitic species) Unionicola 'Haldema.n 1842. 



58 (ss) Without swimming-hairs S9 



