THE AMERICAN CRAB INDUSTRY 613 



During this stage it swims freely, but may also walk on the bottom. The megalops 

 does not moult, except to assume the true crab shape. 



In passing from the megalops stage to the adult crab stage the crab moults 

 about 15 times at intervals averaging approximately 15 days. During this period 

 it increases from ¥25 of an inch in width to about 7 inches, expanding about /^ at 



(.Courtesy U. S. Fish and Wildlife Service) 



Fig. 29-3. The blue crab sheds its old shell. Even when partially 

 out its size is noticeably larger than the old shell. 



each moulting. Growth is rapid, and the crabs mature and mate at the age of 

 12 to 14 months during the second summer. Mating occurs in the female at the 

 time of the last moulting while she is still soft. She is carried tightly by the male 

 for a few days prior to such moulting, and at this stage "doublets" or mating 

 crabs are often caught on the trotlines. If mating occurs early in the summer, 

 the eggs are laid about 2 months later; when the mating occurs in July or August, 

 the eggs are not laid until the following spring or summer. The female crab may 

 lay 2 or more batches of eggs during her lifetime. Most crabs hve only 3 years 

 although a few survive for 4 years. 



Young crabs possess the power of regenerating a leg or claw lost or volun- 

 tarily thrown off. The regeneration is completed at moulting. 



Blue crabs are scavengers and cannibals although they occasionally feed upon 

 aquatic vegetation; their favorite food, however, is the flesh of dead and putrid 

 animals. 



