THE HABITS OF CAMBARUS. 



J. ARTHUR HARRIS. 



It is the purpose of the present paper 1 to present in a brief 

 way some of the main points which have been collected on the 

 habits and distribution of North American crayfishes. 



Our crayfishes offer a particularly inviting and important field 

 for ecological work. A fuller knowledge of the habits of the 

 different species may contribute to a more complete under- 

 standing of the very remarkable sexual dimorphism occurring in 

 the adult males. Individual variability in the species of Cam- 

 barus is very great and puzzling, and the differentiation into 

 species as compared with the other genus Astacus, of the sub- 

 family to which it belongs is extensive. The great differences 

 in environment to which the species are subjected is apparent to 

 anyone who is acquainted with the physiographic conditions 

 prevailing in the vast stretch of territory over which this genus 

 is distributed and an examination of these conditions and the 

 adaptation of the animals to them would doubtless yield interest- 

 ing results. 



The habits of any species necessarily depend largely upon the 

 character of its environment, and from an ecological or biological 

 standpoint it is impossible to consider the two separately. In 

 this place space cannot be given to a discussion of the importance 

 of a correlation of physiographic features with floral and faunal 

 distribution as it lias been emphasized by Woodworth, Hays and 

 Campbell. Simpson. Cowies, Adams and others. 



It has long been known that the fishes occurring in the upper 

 course of a stream of considerable size are different from those 

 found in its lower course, and more recently the ecological factors 

 concerned have been more fully discussed. In the crayfishes as 

 in fishes the Fauna of different parts of a stream is not the same, 



1 This is an abstract of a part of an ecological catalogue of the crayfishes 



