CRAYFISHES OF NEBRASKA AND EASTERN COLORADO 
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small, ranging from 2 to 4.5 millimeters in length,. Pierantoni (1912), quoted by 
Hall (1915), states that this family ranges in length from 1 to 12 millimeters, with 
a max im um width, when in a moderate distension, not to exceed one-tenth of the 
body length. 
The cocoons are quite conspicuous, being about 3 millimeters in length and 
fastened to the body of the host by a narrow stalk. It was formerly thought that 
these might be the eggs of Corixia, the giant water beetle, but their relationship 
to the parasitic worms is now known. Likewise, it was not known for a time 
whether they were to be considered parasites on the crayfish or messmates with 
it. Hall (1915) regards them as parasitic in the adult stage. “They are not 
parasitic when young, a study of the intestinal tract at this period showing vege- 
table detritus and small animals. In the adult stage the teeth are used to break 
the skin of the host animal in order to suck the blood. I have found several pieces 
of striated, voluntary muscle fiber in the intestine of the adult discodrilid described 
in this paper.” 
Ellis (1920), in a revision of the Branchiobdellidse in the United States National 
Museum, records the species found on the Colorado and Nebraska crayfishes. 
The Nebraska species collected during this investigation have not yet been identi- 
fied. Cambarus diogenes was found to be host to Cambarincola macrodonta Ellis 
and C. philadelphica Leidy, the former species only being found on C. diogenes 
from four localities in Colorado, and C. philadelphica being found by Ellis at Rhine- 
lander, Wis. Cambarus immunis and C. virilis from Colorado, and C. propinquus 
from Douglas Lake, Mich., were host to Cambarincola vitrea Ellis. C. propinquus 
from Irondale, Ind., is host to Xitonodrilus formosus Ellis, and the same species 
from Bloomington, Ind., is host to C. philadelphica Leidy. Cambarus virilis, from 
Rolla, Mo., is host to C. chirocepliala Ellis and also to Cambarincola vitrea Ellis 
and the same species from Douglas Lake, Mich., is host to C. philadelphica Leidy. 
It is thus seen that the parasites have not developed into specific form along 
with the differentiation of the host species and seem to show no selection of hosts. 
There is no record of one specimen being host to two species of parasites, though 
the same species of crayfish in different localities may harbor at least three different 
parasites. 
ECONOMIC IMPORTANCE 
Although very abundant in these two States, especially in Nebraska, the cray- 
fishes have received very little attention as regards economic importance. Personal 
inquiry at the office of the game and fish department of Nebraska, at Lincoln, 
brought the information that crayfishes were worth nothing and could not be con- 
sidered among the resources of the State. 
Careful investigation shows them to be of no inconsiderable value in the life 
balance of our streams and meadows. Shelford (1913) has shown that they play 
a definite part in the equilibrium of the fresh-water community, feeding upon the 
decaying vegetable matter, the larger aquatic insects (probably those that have 
died), and possibly the young of frogs and fishes. They, in turn, serve as food for 
the bullheads, the young and the adult black bass, and possibly also for other 
forms. 
