CRAYFISHES OF NEBRASKA AND EASTERN COLORADO 
101 
and “in badly infested areas, near Muldoon, Miss., there are from 8,000 to 12,000 
holes to the acre.” (Fisher, 1912, p. 322.) The name of the species was not re- 
corded, but it destroyed a great deal of the young cotton and corn crop, tearing the 
cotyledons and young leaves and carrying them to their burrows. 
In the irrigated districts of Colorado crayfishes are very plentiful, the burrows 
of C. diogenes being seen along the banks of the ditches where they run their complex 
underground tunnels, often causing breaks in the bank of the ditch. A single alfalfa 
field inspected near Boulder has a great number of burrows of this species extending 
from 1 to 3 meters from the bank of the ditch, the young crop in this strip being 
quite destroyed. 
Cambarus diogenes has become a very great nuisance on the campus of the 
University of Colorado at Boulder. The young entered an artificial pond by way 
of a small inlet stream, and the following autumn dug many burrows in the em- 
bankment on the north side of the pond. A cement wall, which was placed 
along this bank, extending to a depth of 2 feet below the usual water level, has 
eliminated the attacks of the crayfishes at this point. 
The crayfish may be exterminated in a given locality, according to Fisher 
(1912), by using carbon bisulphide, chloride of lime, or calcium carbide. I believe 
that this would suffice for a single season only, and that with the migration of the 
following spring the population would be renewed. 
SUMMARY 
This study of the genus Cambarus of Nebraska and eastern Colorado sum- 
marizes the literature dealing with crayfishes of the area, paying special attention 
to the previous records and giving a redescription of the eight species. The geo- 
graphical distribution is considered and the ecology of the species studied with 
evidence gathered in a field investigation for two consecutive seasons. Life history 
data are gathered, which demonstrate the existence of geographical differences in 
time of copulation and spawning, and suggestions are offered for more detailed 
observations regarding these differences. The literature on discodrilid parasites of 
the crayfish has been reviewed and the suggestion made that the generic and specific 
differentiation of these parasites has been independent of the evolution of the host 
species. Information regarding the economic value and the food relationships is 
presented. 
BIBLIOGRAPHY 
Abbott, Charles C. 
1873. Notes on habits of certain crawfish. American Naturalist, Vol. VII, pp. 80-84. 
Salem, Mass. 
Andrews, E. A. 
1895. Conjugation in an American crayfish. American Naturalist, Vol. XXIX, pp. 867-873. 
Philadelphia. 
1904. Breeding habits of crayfish. American Naturalist, Vol. XXXVIII, No. 447, March, 
1904, pp. 165-206. Boston. 
1906. Egg-laying of crayfish. American Naturalist, Vol. XL, No. 473, May, 1906, pp. 
343-356. Boston. 
1910. Conjugation in the crayfish, Cambarus affinis. Journal of Experimental Zoology, 
vol. 9, 1910, pp. 235-264, figs. 1-8. Philadelphia. 
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