234 Illinois State Laboratory of Natural History. 



lamella on the upper spine of this margin, and the small 

 spine on the apex of the segment are all omitted, hi the 

 figures of the fifth pair of legs of the male, the small spines 

 at the outer apical angles of the segments of both outer rami, 

 the spine at the inner apical angle of the last segment of the 

 right outer ramus, and the hairs on the inner margin of the 

 first segment of both inner rami are wanting. 



Although this species is widely distributed, — having been 

 found in Alabama, Illinois, Minnesota, Oregon, and Wyo- 

 ming, — no differences sufficient to establish even a new 

 variety have been found in specimens from these localities 

 so widely separated and so varied in character. Herrick, in 

 his papers, states that all the specimens examined by him, 

 from Alabama to Minnesota, had 24-segmented antennae. 

 Forbes found the antennae 23-segmented, de Guerne and 

 Richard, who examined specimens sent to Poppe by Forbes, 

 agreed with him, and the writer also found the antenna? of all 

 the specimens lie examined to be 23-segmented. The speci- 

 mens collected by Dr. Forbes in April, 1877, and described in 

 1882, were uniform pale brown; those collected by the 

 writer at Havana, 111., in July, 1896, were hyaline or opal- 

 escent white; while a single male found in June, 1897, at 

 Urbana, 111., in a temporary pool, was bright scarlet through- 

 out, and hardly to be distinguished from the specimens of 

 I), sanguineus among which it was found. Herrick has found 

 Osphranticum in "estuaries of running water," and says that 

 according to his observations it prefers such localities. The 

 writer's observations tend to confirm Forbes's statement 

 that it prefers swamps and pools, or at least quiet or stag- 

 nant water. At the Biological Station at Havana, during 

 the summer of 1896, a single specimen was captured in the 

 Illinois River, in midstream, while in Quiver Lake, in a mat 

 formed of Ceratophyllum and Lemna in a stagnant portion 

 near shore (substation C), they were comparatively numer- 

 ous, though not occurring in any such numbers as either 

 I >i<t]>h>nni* or Cyclops. In fact, in none of the collections 

 examined were they at all common. 



Prof. Forbes, in connection with the original description, 



