ORTMANN: THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 469 



again further down. This is generally seen in the Ohio below Pittsburgh. Although 

 the Ohio collects all the badly polluted streams of western Pennsylvania, it is itself 

 not unfavorable to crawfish life. The best instance for this is the Cheat River. At 

 Cheat Haven, Fayette County, this river is rather clear and teems with life, craw- 

 fishes and Unionidx being abundant. 1 was therefore astonished at the condition 

 of this river at Parsons, Tucker ( 'ounty, West Virginia. The water there has a foul 

 smell, and is utterly unfit for life, which is due to a wood-pulp mill just above Par- 

 sons on Shavers Fork. Between Parsons and Cheat Haven (about fifty miles) the 

 water has improved so far that life is not only possible, but is abundant, only the 

 blackish color of the water remaining as the last result of the contamination. 



V. LIFE HISTORY. 



Only a few scattered notes have been published on the life-history of any of the 

 American species of Camharus, and some of them are ratliei- doubtful. The most 

 complete account is that given by Andrews (1904) on the breeding habits of C. limo- 

 bi.i^, but even this comprises only a small part of the life-history, and moreover, as 

 may be seen below, is in part rendered unreliable by the fact that the observations 

 were not made in the field, but in the laboratory. 



My own observations have been almost exclusively made in the field, and were 

 only occasionally supplemented, or rather confirmed, in the laboratory'. Since it 

 was my object from the beginning to watch the behavior of the crawfishes under 

 natural conditions, laboratory-work could not be depended upon, unless controlled 

 by field-work, and thus the former was neglected altogether. 



With the exception of January and Februaiy,'^^ ni}' work in Pennsylvania extends 

 over the whole year, thus including all seasons. The results are rather satisfactory, 

 and I am able to give a complete account of the seasonal life of no less than four 

 species, and by comparison with these the life-history of the other species of this state 

 may be inferred. Of course I have not been able to solve all questions. For 

 instance the question of the frequenc}' of moulting in one and the same individual 

 remains open, since it can only be settled by observing the same individual contin- 

 uously ; but this is impossible in the field. Nevertheless I have found means to 

 elucidate this question in other ways, although not with absolute accurac}'. 



The most numerous and most complete records I possess refer to the common 

 river-species of western Pennsylvania, C. obscurua, and of this I shall first give an 

 account. 



"From New Jersey I possess observations nintle even in January ami February and referring to C. blandingi, ('. 

 limosus, and C. bartoni. 



