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THE AMERICAN NATURALIST [Vol. XLVI 



I have found females but one year old with eggs, and the 

 development went on in the laboratory just as in the more 

 mature females. The largest female that I captured was 

 102 mm. in length. The largest male was 90.5 mm. long. 



Food. 



Crayfish are omnivorous. I have previously shown 

 that C. bartonius bartoni prefers fresh animal food to 

 stale animal food or either fresh or stale vegetable 

 food (21). 



Some crayfish eat a great deal of vegetable matter, 

 one species, the chimney builder, Cambarus diogenes, 

 seeming to prefer it. The vegetable matter eaten con- 

 sists of dead leaves, potato, onion, young corn and 

 buckwheat. 



The animal food consumed by the crayfish consists of 

 worms, insects, insect larva?, a few fish, frog, toad and 

 salamander eggs, and occasionally a dead fish or frog. 

 I have seen crayfish devour a hapless relative who was 

 endeavoring to rid himself of his old shell. Sometimes 

 females eat eggs from their own abdomens and even 

 devour their own freed offspring. 



Enemies. — The crayfish suffers from internal and 

 external enemies. Among the plants which live symbiot- 

 ically with the crayfish are diatoms, bacteria and sapro- 

 legnia. Internally, Distoma cerrigerum and Branchiob- 

 della have been noted. But these are not all the enemies 

 of the crayfish. Besides man, who uses thousands of 

 dollars worth of crayfish for food and as a garnish, many 

 small animals find them palatable. 



Many fish, including the black bass, Micropterus, 

 which fishermen find very partial to crayfish, eat them. 



Professor Surface reported (38) that the salamanders 

 Cryptobranchus allegheniensis and Necturus maculosus, 

 are among the chief enemies of the crayfish. 



Ortmann mentions seeing the water snakes, Natrix 

 sipedon and A 7 , lebens, when captured, disgorge crayfish 



