220 



ZOOLOGY 



at nineteen. In this latter class are placed the crayfish, lobster, 

 blue crab, shrimp, and most of our common crustaceans. 



The North American Lobster. — In structure it is almost the 

 counterpart of its smaller cousin, the crayfish. Its geographical 

 range is a strip of ocean bottom along our coast, estimated to 



vary from thirty to fifty miles in width. 

 This strip extends from Labrador on 

 the north to Delaware on the south. 

 The lobster is highly sensitive to 

 changes in temperature. It migrates 

 from deep to shallow water or vice 

 versa according to the temperature of 

 the water, which in winter is relatively 

 warmer in deep water and cooler in 

 shallows. Sudden changes in the 

 water of a given locality may cause 

 them to disappear from that place. 

 The more abundant food supply near 

 the shore also aids in determining 

 the habitat of the lobster. Lobsters 

 do not appear to migrate north and 

 south along the coast. While little is 

 known about their habits on the ocean 

 bottom, it is thought that they con- 

 struct burrows somewhat like the cray- 

 fish, in which they pass part of the 

 time. As they have the color of the 

 bottom and as they pass much of their time among the weed- 

 covered rocks, they are able to catch much living food, even 

 active fishes falling prey to their formidable pinchers. They move 

 around freely at night, usually remaining quiet during the day, 

 especially when in shallow water. They eat some dead food; and 

 thus, like the crayfish, they are scavengers. 



Development. — The female lobsters begin to lay eggs when 

 about seven inches in length. Lobsters of this size lay in the 

 neighborhood of five thousand eggs; this number is increased to 

 about ten thousand in lobsters of moderate size (ten inches m 



North American Lobster. This 

 specimen, preserved at the U.S. 

 Fish Commission, was of un- 

 usual size and weighed over 

 twenty pounds. Notice the 

 chelipeds. 



