CHAPTER XI 

 THE CRAYFISH AND ARTHROPODS IN GENERAL 



i. THE CRAYFISH 

 (Cambarus wrilis Girard) 1 



CRAYFISHES inhabit fresh-water lakes, ponds, and streams. 

 The species Cambarus mrilis is common in some of the central 

 states and Cambarus affinis in the eastern part of the country. 

 The lobster is so nearly like the crayfish in structure that the 

 anatomical portion of this chapter may be applied also in large 

 part to this animal. In Europe the most common crayfish is 

 As focus fluviatilis, a species made famous by Huxley's classical 

 work " The Crayfish." 



The crayfish, Cambarus mrilis, is usually found concealed under 

 rocks or logs at the bottom of ponds and streams. Here it lies 

 with its head toward the entrance to its hiding place. When 

 crawling about or swimming in the open water, its hard shell 

 helps protect it from fish, while its color, which resembles the 

 bottom, tends to make its detection difficult. Crayfishes may be 

 captured easily by hand, with a net, or by fishing for them with a 

 string baited with a piece of meat. They thrive in an aquarium, 

 and their entire life history may be observed in the laboratory. 

 The yearly decrease in the number of lobsters available for food, 



1 The complete life history, and the details of the anatomy are not known for 

 any single species of the genus Cambarus. The following account, therefore, 

 must necessarily be a composite containing not only observations on various 

 species of Cambarus, but also on the European crayfish, Astacus (Potamobius) 

 fluviatilis. The differences between these crayfishes are, however, so slight 

 as to be of little importance except in a detailed monograph, 

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