COPEPODS OF THE WOODS HOUE REGION 93 



Female. — One of the smallest species; head fused with first seg- 

 ment; fifth segment more or less separated from the fourth, with 

 rounded posterior corners, each armed with a minute spine; genital 

 segment longer than the abdomen,' with a small spine at the center 

 of each lateral margin ; caudal rami twice as long as wide ; spines on 

 first basipods of fifth legs minute; endopods rudimentary and un- 

 armed; hook on second exopod segment nearly straight; third exo- 

 pod segment represented by 2 or 3 spines, the inner one the longer. 

 Total length, 0.9-1.15 mm. 



Male. — Antepenultimate segment of right first antenna with a slen- 

 der finger process at its outer distal corner, which often reaches 

 the tip of the end segment; second basipod of right first leg sub- 

 quadrate, longer than wide, the lateral spine at the center; second 

 exopod segment twice as long as the first, its lateral spine nearer 

 the base ; right endopod a mere knob ; left endopod reaching beyond 

 the center of the end segment of the exopod and unarmed; exopod 

 terminating in a fingerlike process, the end segment with a sinuous 

 inner margin fringed with hairs. Total length, 0.9-1 mm. 



Remarhs. — The females carry from two to six eggs; when even, 

 the eggs are arranged in pairs; when odd, the single egg is pos- 

 terior to the others and between them. In the Upper Cotuit Pond 

 none of the specimens showed any red but were all pale brown or 

 colorless, and the majority of them were covered with algal growths. 

 In the Lower Cotuit Pond 80 per cent were bright red, and not a 

 single one showed algal growths. This is a northern form, which 

 comes a little farther south near the Atlantic coast than it does in 

 the Mississippi Valley. It may be recognized most easily by its 

 small size and by the structure of the fifth legs in both sexes. 



DIAPTOMUS SANGUINEUS Forbes 



Figure 63 



Diaptomus sanguineus Foebes, Bull. Illinois Mus. Nat. Hist., vol. 1, pp. 15, 

 16, 23, figs. 24, 28-30, 1876.— Maksh, Trans. Wisconsin Acad. Sci., vol. 15, 

 p. 478, pi. 25, figs. 2, 5, 8, 1907. 



Occurrence. — Twenty specimens, including both sexes, were 

 obtained from a small ice pond on Cuttyhunk Island, July, 1926. 



Distribution. — Found quite generally in the Mississippi Valley as 

 far east as New York, as far north as Wisconsin and Minnesota, as 

 far west as Nebraska, and as far south as Alabama (Marsh) ; 

 Wellesley and Medford, Mass. (Forbes). 



Color. — Transparent with a decided azure-blue tint, deepest at the 

 bases of the swimming legs and along the grooves between the seg- 

 ments; ovaries and oviducts blood red, showing very prominently 

 through the body walls ; first antennae yellow ; eye deep carmine-red. 

 71937—32 8 



