862 



FRESH-WATER BIOLOGY 



15 (16) Genital flaps present, acetabula 3, knob-like. 



Panisus Koenike 1896. 



Similar to the preceding in appearance; with chitinous 

 plates more or less developed, in our one described species 

 covering most of the dorsal surface. One species, P. cata- 

 phractus, described by Koenike (1895) from Canada, about 

 1.2 mm. in length. 



Fig. 1327. Panisus calapkra^-tus (Koenike). Epimeral area, 

 genital area and ma?dllary shield. X 43. Outer side, left palpus. 

 X 93. (After Koenike.) 



16 (15) No genital flaps; numerous stalked acetabula. 



Sporadoporus Wolcott, 1905. 



A red mite with body beset by small conical 

 papillae; capitulum produced into a slender snout. 

 One American species, not yet described, known so far 

 only from Yellowstone Park, a little under medium 

 size. 



Fig. 1.328. Sporadoporus invalvaris (Piersig), a European 

 form. Ventral surface, female. X 3i' Palpus. X 123. 

 (Modified from Piersig.) 



17(12) With swimming-hairs Hydrypkantes^odni^T,']. 



A brownish-red mite, with a median eye 

 surrounded by a large chitinous plate; 

 adapted to more open water. Species 

 several, and occurring frequently. A little 

 above medium size ranging from 1.2 mm. 

 to about 2.2 mm. 



Fig. i32g. Hydryphantes ruber (de Geer), a 

 European species. Ventral surface, female. 

 Xi7-. Outerside, left palpus, of female. X42. 

 (Modified from Piersig.) 



