over carefully and promptly discards any that fail to develop properly. Unlike 

 the lobster and many other crustaceans, the crayfish does not go through a series 

 of developmental stages that may recapitulate the evolutionary history, but 

 starts its free life as a miniature of its parent. 



Crayfishes make interesting aquarium pets. Those from ponds or slowly 

 moving water naturally live better under aquarium conditions than those from 

 swift streams. For best results the container should be arranged so that the 

 crayfish may emerge from the water when it so desires. As a matter of fact 

 many crayfishes spend a good deal of the night at the very edge of the water 

 or out on the mud flats. The raccoons know this and profit by it. As long 

 as the gills remain moist the crayfish can survive, and most fishermen have 

 learned to carry their bait crayfish in damp moss rather than in water. At 

 the time of the shedding of the skin, which splits across the back and enables 

 its occupant to "jack-knife'' out, a captive crayfish should be removed from 

 its fellows, so that they cannot profit by its helplessness to make a meal of it. 



Crayfish are omnivorous and all is grist that comes to their mill, be it dead 

 or alive, plant or animal. Undoubtedly they play an important part in the 

 economy of nature, cleaning up all waste and becoming in their turn food for 

 other animals. 



KEY TO THE ORDERS OF CRUSTACEA 



1. Small or microscopic animals; body without appendages on the abdomen 



or enclosed within a bivalve or apparently bivalve shell — Subclass 

 Entomostraca 2. 



Large or small but not usually microscopic; with legs or modified ap' 

 pendages on the thorax and the abdomen; no bivalve shell — Subclass 

 Malacostraca 5. 



2. No bivalve shell; with cylindrical, twcbranched thoracic appendages 



(or much modified in parasitic forms) 

 Copepoda Copepods 

 With an actual or apparent bivalve shell or with flattened or simple 

 thoracic appendages 3. 



3. With a bivalve shell enclosing the animal, resembling a tiny clam; less 



than four pairs of body appendages 

 Ostracoda Ostracods 

 No clam-like shell — or, if so, with five or more pairs of body appendages 



4. 



4. With five or six pairs of body appendages; body indistinctly segmented 



Branchwpoda, Suborder Cladocera Water Fleas 

 With eight or more pairs of body appendages; body distinctly segmented 

 Branchiopoda, Suborder Phyllopoda Phyllopods or Fairy 

 Shrimps 



5. No carapace or shell 6. 

 With a carapace 7. 



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