236 ELEMENTARY ZOOLOGY. 



254. The Relatives of the Crayfish (Crustacea). In 

 this division belong the lobsters (Fig. 81), crabs, shrimps, 

 barnacles, water-fleas, and sow-bugs. The most of 

 them are marine; but the crayfish and a number of 

 species of much smaller types live in fresh water, and the 

 sow-bug and pill-bug are air-breathing. They have a 

 thicker covering than spiders and insects, as a rule. 



The lobsters are quite similar to the crayfish in every- 

 thing except size. They are marine and are found along 



FIG. 80. Larva of lobster (Homarus americanus") removed from egg shell. From 

 Herrick. 



Questions on the Figure. Compare with the adult (Fig. 81) and 

 note similarities and differences. Examine Dr. Herrick's figures 

 (Bull. U. S. Fish Commission for 1895), and notice the gradual 

 change to the adult condition by successive moultings. What 

 structures can you identify? 



all our coasts. They feed upon various slow-moving 

 invertebrates and upon dead fish. It is claimed that they 

 are able to capture living fish also. They are often colored 

 in such a way as to harmonize with their surroundings 

 and this aids in the capture of their prey. The lobsters 

 stand next in importance to the oyster as an invertebrate 

 food-species for man. It has been captured in such 

 numbers during the last twenty years that it is in danger 





