ORTMANN: THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 485 



always keep moving. Diogenes also wanders across country at this time, in day- 

 light as well as at night. I have found several crushed in wagon roads. Under 

 these circumstances I have yet to find a feraale." In another letter Mr. Williamson 

 says pertinently that the specimens taken by him in spring in open ditches are all 

 old males, "in which the death instinct had developed." 



Thus it seems evident that the western form does not agree with the form found 

 in Pennsylvania in so far that in early spring the specimens seem to habitu- 

 ally leave their holes. Whether it is only old males when about to die (analogous 

 to what we observed in the case of C. obscurus) which wander about, or whether the 

 females with eggs also are found in open water, and furtlier, whether copulation 

 normally takes place in spring, are assumptions which remain to be proved. The 

 observations of Bundy, Hay, and Harris are surely correct, but it remains to be 

 ascertained whether they represent exceptional cases, or whether they are the rule. 

 Moreover it is not improbable that in the western form the seasonal cycle is slightly 

 different, since it lives under somewhat different surroundings. Hay (1896, p. 491) 

 reports that during the dry months of the summer C. diuyenes seems to lie at the 

 end of the burrow (which contains hardly any water) in a sort of a stupor. I never 

 observed anything like this in Pennsylvania, the holes of C. diogenes being always 

 well filled with water at the bottom, and the crawfishes being very lively. 



That observations on the habits of this species should always be considered care- 

 fully with reference to all accompanying facts is evident from the following case : 

 Dr. D. A. Atkinson found a number of specimens on April 20, 1905, in open pools 

 near Westview, Allegheny County, Pennsylvania, in a region where this species is 

 abundant. These pools were in the course of an old, abandoned mill-race, which 

 dried out late in summer. All these specimens, seven in number, were young, 

 measuring from 33 to 5'2 mm. in length, and consequently belonging to the genera- 

 tion of the previous year. Now, bearing in mind the fact tlijvt the late summer and 

 fall of 1904 and also the winter of 1904-5 were characterize*l in our region by an 

 extreme lack of precipitation so that all streams were exceptionally low till the 

 middle of March, 1905, when a flood (March 20 to 25) restored the normal condi- 

 tions, it is very likely that this mill-race was dry in the summer and fall of 19(»4, 

 when these young specimens began to make their own burrows. They selected this 

 place as a favorable one, and remained there all through the winter, a few snialler 

 floods, one on .January 13 and another on March 9, not disturbing them, till tiie big 

 flood filled the mill-race again for a longer time, Such conditions, iiowever, do not 

 suit this species, and consequently the specimens came out of their holes, and were 

 found, at least for a time, in the open pools, till they had selected more convenient 



