ORTMANN : THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 473 



very large females are rare in the latter part of June and in July, and do not become 

 more abundant till the beginning of August. In addition we now have a new genera- 

 tion of young crawfishes, hatched at the end of May and beginning of June. After 

 these have left the mother it is difficult to get them. They are too small, and are 

 often overlooked, and if captured in the net. are able to e.scape through the meshes. 

 I)Ut I have seen them at this time, although the first recorded captures are as late as 

 July 10, 1900 (by Dr. D. .\. .\tkinson), size 26 mm., and July 24, 1905 (by myself), 

 size 21 to 23 mm. This young generation is easily distinguished from the rest by 

 its size, being considerably less than 30 mm. in length. The minimum length of 

 crawfishes in spring is 31 mm. in the case of males and 27 mm. in that of females. 



In the middle of July further changes occur. A new period of moulting begins 

 for the medium-sized and older individuals, which is chiefly noticeable among the 

 males, since they now again as.sume the first form. The earliest date for the new 

 males of the first fcjrni is .Inly 11, 1905 (Tionesta and Spartansburg). Altogether 

 four individuals were taken, all of which had soft shells, showing the fact that they 

 had recently moulted. Further dates are July 24, 1905 (Deer Lick), July 

 25, 1906 (Russelton), July 26, 1904 (Deny), July 27, 1906 (Shousetown), and 

 then in August and the following months they regularly occurred. At first 

 these males of the first form are scarce, but they become gradually more fre- 

 quent, till finally at the end of September and in October almost all males have 

 assumed the first form. This also holds good fur the new generation born at the 

 end of May and tlie beginning of June. These young ones are about 20 to 23 mm. 

 long in July; in August I have specimens from 24 to 39 mm. in length; in Sep- 

 tember from 26 to about 50 mm. in length. About this time this generation l)e- 

 comes obscured ; for it seems that the rate of growth of the young crawfishes is very 

 different in different individuals, some gaining during June, August, and Septeml»er. 

 only about 15 mm. in length, others more than twice that length. They are al>out 

 10 or 11 mm. long when they hatch. The same fact was observed by Andrews 

 (1904, p. 202) in C. Iimom.% with even greater differences in size (the length of the 

 young of the same generation in October being between 22 and 60 mm.). 



It is ascertained from the above observations that young specimens, born in 

 early sununer, already at the end of the first summer (Septemlier and October) 

 reach a size sufficient to prepare them for propagation, and the males of this genera- 

 tion as a rule show this by changing into the fii^st form. The smallest male of the 

 first form, collected by my.self in fall (October 6, 1905), is a specimen from Kittjui- 

 ning, 38 mm. long, but specimens from 40 to 50 mm. long, and undoubtedly belong- 

 ing to this generation, are quite abundant at this time. Thus we see that by October 



