96 
BULLETIN OF THE BUREAU OF FISHE RIE S 
Fig. 2. — Diagram of barrow of 
Cambarus immunis in bank 
of permanent pond. Length 
of burrow, 40 centimeters. 
Wavy line indicates water 
level. X marks place where 
specimen was taken 
Fig. 3.— Diagram of burrow of Cambarus 
immunis beneath a stone in a temporary 
pond. Length of burrow, 14 centimeters. 
Wavy line indicates water level. X marks 
place where specimen was taken 
the evening after sunset. At Hanlon, Nebr., on June 17, I found a small pasture 
pond that was rapidly drying up. After 6.30 in the evening signs of activity were 
noticed, and many individuals were seen bringing pellets of earth in the manner 
described by Ortmann (1906), and depositing them on the 
rim of the chimney. This unusual midseason activity in 
burrows already over 20 inches in depth was probably due 
to the influence of the drying up of the pond and the 
necessity for the crayfish to find water at a lower level. 
The animals were found in burrows during the day, but in 
the evenings large numbers 
were present in the open 
water. I saw many speci- 
mens, also, in the streams 
near the pond colonies, al- 
though I did not find them 
in burrows on the banks of 
these streams. I have found 
several colonies of this 
species in Colorado living in 
a clay soil on a series of 
alkali flats. Although several similar soils are known in eastern Nebraska, not any 
of them were inhabited by any species of crayfish. 
Cambarus diogenes is perhaps the most interesting form of Nebraska crayfish. 
Although reported by writers to be an inhabitant of the ponds with C. immunis, 
several hundred collections have failed to give a single diogenes from any area save 
the clear creeks and smaller rivers. A few were 
taken from the Empire reservoir, a large artificial 
lake near Greeley, Colo. I have taken a few 
specimens from the creek bed in the evening, but 
most of my species 
have been ob- 
tained from the 
long and complex 
burrows which 
they make (fig. 4) . 
An unusual in- 
stance of this well- 
digging habit is 
shown in Figure 5. 
The burrow is not 
deep, but had been 
Fig. 4. — Diagram of barrow of Cambarus di- 
. ogenes in the bank of an irrigation ditch. 
Total length of tunnel, 125 centimeters. 
Wavy line indicates water level. X marks 
place where specimen was taken 
Fig. 5. — Diagram of burrow of Cambarus di- 
ogenes in disintegrated limestone on the bank 
of a creek. Depth of well, 30 centimeters. 
Wavy line indicates water level. X marks 
spot where specimen was taken 
dug through several inches of disintegrated limestone, ending on a harder terrace of the 
same material. The chimney was asymmetrical, with particles of stone cemented 
by the mud from the same excavation. In western Nebraska, at Valentine, I found 
large numbers of this species that had made burrows in the side of a steep bank of 
sandy loam, which formed the bank of Minichaduza Creek. No chimneys were 
present, although usually so distinctive a part of the diogenes well. This again is 
