TEMPORARY POND COMMUNITIES 179 
early freezing and cold weather followed by warm weather of a very 
springlike character in December. Professor Child observed that the 
Eubranchipus hatched during this period of warm weather. Cold weather 
came on soon after and most of those that had hatched died before 
reaching sexual maturity, and for several years after the species was 
very scarce in the vicinity of Chicago. Eubranchipus is found only in 
grassy ponds, possibly because the forested ponds do not dry sufficiently 
in summer. We have found it on one occasion in woods, but this was 
THE BARE SAND WATER MARGIN AND INHABITANTS 
Fic. 133.—Margin of Lake Michigan at Buffington. 
Fic. 134.—The beach tiger-beetle (Cicindela hirticollis); 1 times natural size. 
Fic. 135.—The beach ground beetle (Bembidium carinula); 1} times natural size. 
in flood-plain pools following an early spring flood and might have been 
due to the washing-in of eggs or young. 
c) Forest temporary pond sub-formation (association) (Station 50; 
Table XXXVII).—These are characterized by the absence of both 
Diaptomus and Eubranchipus. The Entomostraca are chiefly ostracods, 
such as Cyprois marginata, which occurs in grassy ponds. Vortex, mos- 
quito larvae, the little bivalve (Musculium), small earthworms (Lum- 
briculus), and the larvae of a beetle (Dascyllidae) are also very common. 
