ORTMANN: THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 481 



the same conditions. As late as September 5, 1904, (Smithfiekl, Fayette County), 

 and October 6, 1905, (Kittanning, Armstrong County), I found two very small speci- 

 mens (24 and 20.5 mm. long) in small holes. Never after July 19 have I found 

 young ones in the hole of the mother, so that it is quite sure that at the end of July 

 they invariabl}^ shift for themselves when they have attained a length of about 20 

 mm. The largest found in the hole with its mother was 18.5 mm. in length, on 

 July 19, 1905. Since young specimen? found in the same hole, apparently being 

 brothers and sisters, often have a different length (15 to 18.5 mm. in the case just 

 mentioned), and since, as said above, specimens of only 20.5 mm. in length are found 

 as late as October, the rule is established in the case of this species also that the in- 

 dividuals of the same litter grow up at a difierent rate. 



With regard to the presence of males of the first form, the same conditions seem 

 to prevail as in the case of C. obscuriis. These males are frequent in spring. 1 

 found them at the following dates : March 23 ; April 2, 6, 15, 16, 24, 30 ; May 2, 3. 

 13, 14, 21, 22, 27, 29 ; June 2, 15. Then follows a gap of over a month to July 20. 

 Within this period I made observations upon the following dates: June 16, 18, 26. 

 27 ; July 6, 10. At none of these dates did 1 discover a male of the first form. It 

 is true that the material in this species is less abundant, a dozen specimens collected 

 on one day representing a rich luiul ; but it is nevertheless remarkable that during 

 the period just mentioned, in which particular pains were taken to get males of the 

 first form, none were secured. But after this they again appeared regularly, namely : 

 on July 20; August 7, 8, 22, 26; September 5, 7, 15, 19, 21 ; October 6, 9, 11, 18, 

 24 ; November 5. This makes it evident that in early summer (end of June and 

 beginning of July) there is a time when no males of the first form are present. 



However, males of the second form are found at any time in the year as fre- 

 quently as those of the first form. In this respect C. d'wgcnes seems to differ from 

 C. obsciirus. This seems to be due to tlie fact that C. diogenes attains se.xual 

 maturity at a later age than C. obscuru.s and the river species in general. The 

 smallest male of the first form ever found met\sures 55 mm. in length (August i2. 

 1905, Montrose). It is hardly possible that this individual should belong to the 

 generation l)orn in June of the same year, since the latter are known to be at that 

 time about 30 or at the utmost 40 mm. long. We may assume tliat C (Uixjao.^, 

 like C. ohsmrm and C. limosus, may attain at the end of the first summer a length 

 of about 40 or 50 mm., but these individuals do not then assume tiie fii-st form as 

 the river species do. The same is true of the females. The smallest seen in copula- 

 tion (or associated with a male) was 63 mm. long, and the smallest female with 

 eggs was 62 mm. long. 



