
FOOD AND FEEDING 

goldfishes. Another abundant form of live food is Mosquito larve, 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 larve 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. 
CrayrisHes. 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 antenne 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 maxilla, and three 
pairs of maxillipeds or foot-jaws. The 
segments of the thorax under the carapace 
bear a pair of prehensile limbs with chelz 
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- 

i atti eral species, difficult of identification, as 
FIG. 73. Freshwater Crayfish, they all exhibit considerable variation. 
Cambarus blandinii. aaL: ; ; : . } : 
The distribution of the 79 species of 
/ E 
Cambarus is limited to the Atlantic water shed and of the 7 species 
of Astacus to the Pacific water shed. The species most abundant 
from New York to Alabama and south to Virginia are Cambarus blandinii, 
Fig. 73, C. propinguus 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 
123 
