FOOD AND FEEDING 



goldfishes. Another abundant form of live food is Mosquito larvae, which 

 should be here mentioned but is more fully described in another Chapter. 

 Too strong light and changes in the temperature of the water seriously 

 affect the survival of this live food. Experienced breeders guard against 

 these by keeping the pails or tanks in secluded places and provide protect- 

 ing covers. For Goldfishes Daphnia, Cypris, and Mosquito larvae are the 

 best food, preference being given to the former. For the other freshwater 

 fishes all the mentioned Crustacea serve as food ; they may be fed on any 

 of them small enough to be swallowed. 



Crayfishes. These largest freshwater Crustaceans occur abundantly, 

 in most lakes and streams except in the New England states and the Great 

 Plains region. They resemble the Lobster in miniature. The head and 



thorax are amalgamated in one mass 

 covered with a carapace. The abdomen 

 is divided into seven segments, six of 

 which bear swimmerets and the seventh a 

 divided flattened tail-fin or telson. The 

 compound eyes are borne on long movable 

 eye-stalks, behind which are two long 

 jointed antennae and a second pair of short 

 antennules. The mouth is on the under 

 surface and is provided with one pair of 

 mandables, two pairs of maxillae, and three 

 pairs of maxillipeds or foot-jaws. The 

 segments of the thorax under the carapace 

 bear a pair of prehensile limbs with chelae 

 or claws, two pairs of ambulatory or walk- 

 ing legs with smaller claws and two pairs 

 of legs ending in simple pointed extrem- 

 ities. These, together with the swim- 

 merets and telson, constitute twenty pairs 

 of appendages. Most localities have sev- 

 eral species, difficult of identification, as 

 they all exhibit considerable variation. 

 The distribution of the 79 species of 

 Atlantic water shed and of the 7 species 

 water shed. The species most abundant 



FIG. 73. Freshwater Crayfish, 

 Camharus blandinii. 



Cambarus is limited to the 



of Astacus to the Pacific 



from New York to Alabama and south to Virginia are Cambarus blandinii. 



Fig. 73, C. propinquus and C. affinis; but the greatest number of forms 



occur in the southern and central portion of the United States. 



Crayfishes hide under stones or in holes excavated in the banks, where 



1Z3 



