Chapter 12 

 CRUSTACEA 



The Crustacea are divided into a number of orders, most of 

 which are quite easily recognized. The Decapoda, comprising the 

 crabs, lobsters, crayfish, etc., are well known to all. Our repre- 

 sentatives are the crayfish, belonging to the family Astacidae or 

 Potamobiidae. The word crayfish has a curious origin. The 

 old German Krebis, for large Crustacea in general, has become 

 krebs in modern German, and crab in English. But in France 

 the name is applied to the common animal of the streams, and 

 became modified to ecrevisse. This, finally reaching England, 

 was converted into crayfish, which in America occasionally be- 

 comes crawdad. The typical genus of Crayfishes, Astacus, is 

 found from Europe to the Pacific coast region of the United States. 

 But in the Eastern United States, and west to the base of the 

 Rocky Mountains, is a different genus called Cambarus, quite 

 rich in species. This genus also occurs in Mexico, and even has 

 a species in Cuba. Cambarus diogenes of Girard, the name 

 suggestive of its habits, is very common in Boulder. On it 

 was discovered a remarkable parasitic worm, named Cambarincola 

 macrodonta by Ellis. Another crayfish, Cambarus virilis of Hagen, 

 was the host of the worm Cambarincola vitrea of Ellis in the 

 Arikaree River, near Beecher's Island. It is singular that these 

 crayfish worms (Branchiobdellidae), though referable to several 

 genera and numerous species, do not restrict themselves to 

 particular species or even subgenera of Cambarus. One species 

 of worm has actually been found on twelve kinds of crayfish. 

 The Cambarincola macrodonta is common in Eastern Colorado on 

 Cambarus diogenes, but if we go south to Las Vegas, New Mexico, 

 we find an entirely different crayfish, belonging to another group 

 of the genus, one which has Mexican relationships. Naturally 

 we should expect to find here a different worm, but according to 

 Dr. Ellis it is the very same C. macrodonta* 



The Amphipoda are suggestive of small shrimps, with com- 



*A good account of the Colorado crayfishes, by E. T. Engle, appears in Bulletin of the 

 Bureau of Fisheries, XLII (1926). It is regrettable that Engle has published the records of 

 Dr. Ellis in such a manner that no one can tell who collected or identified the specimens. In 

 the case of C. simulans from Kit Carson County we are informed that Faxon made the deter- 

 mination, but no credit is given to Ellis for adding this species to the fauna of Colorado. 



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