220 



COLLEGE ZOOLOGY 



bait. The soft-shelled crayfishes may be 

 kept soft for a week or more on ice. Re- 

 frigeration slows metabolism so that the 

 shell develops slowly. 



The crayfish is used for food, especially 

 in Europe and on the Pacific Coast. The 

 spiny lobster of the Pacific Coast may reach 

 a weight of 10 pounds. Shrimps and prawns 



Figure 123. A Cape Cod lobsterman removing a prize lobster from a wooden trap. These traps 

 are baited, weighted with a brick, tied to the frame, as shown, and set in the ocean to harvest 

 the lobster crop. (Courtesy of Mike Roberts Color Productions.) 



are marine species whose large abdominal 

 muscles are sold in the fresh condition or 

 canned. The shrimp industry in the United 

 States is especially important in Louisiana 

 and California. Certain crustaceans may 

 become pests when present in large num- 

 bers. Thus in some parts of our southern 

 states, crayfishes damage cotton and other 

 crops by devouring the plants; they occa- 

 sionally burrow into levees and weaken 

 them. Sow bugs, which also feed on vegeta- 



tion, may become pests in greenhouses and 

 fields when sufficiently numerous. 



Although some crustaceans are parasites 

 of aquatic animals, none is a parasite of 

 man or other land animals. Copepods serve 

 as intermediate hosts of several parasitic 

 worms in man; for example, certain species 

 of Cyclops for the guinea worm and other 

 species of Cyclops for tapeworms. Crayfish 

 and crabs act as second intermediate hosts 

 for the lung flukes. 



