98 
BULLETIN OF THE BUREAU OF FISHERIES 
died and the young were not raised. It was observed that the “berried” females 
rarely survived laboratory conditions, whereas smaller specimens of both males and 
nongravid females were kept for 10 weeks. 
Further records of gravid females of this species within the vicinity of Lincoln 
were taken on April 29 and May 13. Perhaps the most interesting record was one 
of two C. immunis 40 millimeters in length, taken at Atkinson, Nebr., on October 30. 
One female carried a large cluster of eggs, which were hatching, but both specimens 
died three days later. 
Harris records March 21 as the earliest date for berried females of this species 
in Kansas. This is more than a month earlier than my records for the same 
species in an adjoining State, although I have taken specimens as early as April 1, 
but found no gravid females. 
Herrick (1896) reports a number of females of C. immunis already in berry 
taken at Ann Arbor, Mich., on November 16, when the ice was beginning to form. 
The earliest records for 0. diogenes are May 13, taken at Seward, Nebr., and 
May 30, taken at Boulder, Colo. Harris (1902) reports a female with eggs taken on 
May 3. Pearse (1910) reports a pair copulating in White Pigeon River, Mich., on 
April 13. Hay reports C. argillicola with young on April 2. Ortmann (1906) gives 
April 6 as the earliest records for females of C. diogenes with eggs, and May 21 as 
the earliest date for females with young taken in Pennsylvania. 
Copulation has not been observed in either Nebraska or Colorado species, 
though on June 17, at Hanlon, Nebr., I examined 15 burrows, in 7 of which both 
the male and the female of Cambarus immunis were found in the same burrow but 
not in copulatory position. This is, however, a rare condition, and according to 
Ortmann (1906, p. 482) it is “an absolute rule that under ordinary circumstances 
only one specimen occupies a hole,” and that this association is found only during 
the mating period. That this pond was drying up, owing to an especially dry 
summer, may have had some influence on the time of copulation. 
Ortmann states that the copulating season for C. diogenes falls in the autumn, 
having observed it on October 24 and November 5. At variance with this is the 
record of Hay (1896, p. 491) that C. diogenes was taken in Indiana on April 2 with 
pairs in copulation. 
It is apparent that careful attention should be given to the geographical 
differences in the life history of a single species, studied over a series of years in 
localities of distinct climatic and seasonal differences. 
Young of all these species leave the burrow of the mother and may be taken 
in schools in the open water when from 8 to 20 millimeters in length. At from 18 
to 25 millimeters they begin to dig burrows for themselves, and may no longer be 
taken throughout the day in the open water. 
PARASITES 
In most of the collections of crayfishes in both Colorado and Nebraska a few 
specimens were found that bore the interesting an n elids belonging to the Disco- 
drilidse. On some specimens of C. immunis found near Lincoln the entire carapace 
was covered with the cocoons of this worm, while on the ventral portion, especially 
around the mouth, were many of the mature animals. These annelids are rather 
