HARRIS : CRAYFISHES GENUS CAMBARUS. 63 



color requires some weeks, or possibly months, of time, and 

 that, since many species of crayfish are migratory, especially 

 those living in running water, the color of those seen in small 

 streams may not be at all like their environment, and that the 

 best results may be obtained from a study of those in the small 

 ponds, where migration cannot occur. Until our knowledge of 

 the habits of this genus is much fuller than it is now, one 

 should be careful in stating that many species are migratory in 

 their habits, unless the terms are carefully limited. 



The point in regard to the colors of C. diogenes is especially 

 interesting. It will be noticed that the habits of the species as 

 observed by Mr, Kent are quite different from those usually 

 attributed to it, for it seems usually to occur in the open water 

 for but a very limited part of the year. My observations on 

 C. diogenes are not extensive, but in C. gracilis the females which 

 are found in the open ponds for some time in the spring are of 

 the same olive-green color during the entire period. In the 

 very large series of material I have collected in open water I 

 have never found an exception, nor did the two or three speci- 

 mens I have taken from burrows late in the summer show any 

 differences, but the four or five males, all first-form — the adult 

 second-form not being known — were all of a beautiful salmon-red 

 color, and in all cases I have every reason to believe they had 

 just come from burrows, a point in which I am certain in two 

 cases. Tlie young of both sexes up to an inch and more in 

 length show a coloration somewhat similar to that of the adult 

 female. It is interesting to notice that, according to Faxon, 

 C. carolinus {C. dubius Fax,), another of the burrowing forms, 

 is known to the Indians in the Territory as "red crayfish," and 

 that, according to Williamson ('01), it has, in Allegheny 

 county, Pennsylvania, a very different color. 



In this place the colors of the cave species need not be con- 

 sidered, since this is touched upon under the individual species. 

 It would be interesting to examine the young in reference to 

 the development of color, as has been done in the case of some 

 of the cave-inhabiting fishes. For those who have the oppor- 

 tunity, be it for experimental or field observation, the colors of 

 these animals certainly offer an interesting problem. 



