They could be northern crayfish Orconectes virilis which is superficially similar to the red swamp crayfish, both get large. To be sure of the name you need to pull of the male gonopod and compare it to both species. Red swamp is not reported to occur in Colorado whereas northern crayfish occurs in CO which is why I asked where it was collected.
Last edited by Bill Cody; 08/03/15 11:32 AM.
