Copepods 



189 



The species of Diaptomus are remarkable for having 

 usually very long antennas and often a very lively red 

 color. Sometimes they tinge the water with red, when 

 present in large numbers. 



Copepods feed upon animals plancton and algae, 

 especially diatoms. They are themselves important 

 food for fishes, especially for young fishes. 



The higher Crustacea, 

 (Malacostraca) are rep- 

 resented in ovir fresh 

 waters by four distinct 

 groups, all of which 

 agree in having the 

 body composed of 

 twenty segments that 

 are variously fused 

 together on the dorsal 

 side, each, except the 

 last, bearing (at least 

 during development) a 

 pair of appendages. 

 Of these segments five 

 belong to the head, 

 eight to the thorax and 

 the remainder to the 

 abdomen. Mysis (fig. 

 97) is the sole represen- 

 tative of the most primitive of these groups, the order 

 Mysidacea. Its thoracic appendages are all biramous 

 and vindifferentiated ; and still serve their primal 

 swimming ftinction. Mysis lives in the open waters of 

 otir larger lakes, in their cooler depths. It is a delicate 

 transparent creature half an inch long. 



The Scuds (order Amphipoda) are flattened laterally, 

 and the body is arched. The thoracic legs are adapted 



Fig. 96. A female Cyclops, with eggs. 



