76 ECONOMIC ZOOLOGY 



It is sometimes the custom to pay negroes a barrel of flour or of corn 

 for each barrel of crayfish collected. The Department of Agriculture 

 investigated the problem and found various remedies. Apparently 

 if they are persistently hunted at twilight, at night, or after a rain, 

 they may be exterminated or so reduced in numbers as to be of little 

 harm. The easiest way is to pass along the rows and systemati- 

 cally kill them with clubs or by stepping on them. If instead of this, 

 they be collected, they may be either sold as food for man or they may 

 be boiled, mixed with meal, and allowed to dry, when they make most 

 excellent chicken feed. 



There are various poisons that when introduced into the holes 

 and then filled in, will destroy the animals and leave them buried. 

 Chlorid of lime, (one pound to three gallons of water) is effective 

 and cheap, but the mixing and hauling may make it as expensive 

 as carbon bisulphid, which may be introduced into the hole with 

 a long oil can, such as locomotive engineers use, after which the hole 

 is closed by stepping on it. The cost of the carbon bisulphid will 

 be from $i to $2 per acre, or perhaps more in times of high prices, and 

 the cost of the labor will perhaps be greater than the cost of the poison. 



Crabs. There are many kinds of crabs that are used for food by 

 man. In the tropics several forms of land crabs are thus used, some of 

 them being collected in large numbers as they migrate from the 

 mountains to the sea to spawn. 



In the United States it is the strictly aquatic forms, Callinectes 

 and others, that are used, Fig. 54. These are used both as "hard- 

 shell" and as "soft-shell" crabs; the former is the crab in its normal 

 condition with the hard, chitinous exoskeleton; the latter is simply 

 a crab that has recently molted, whose exoskeleton has not yet 

 hardened. The hard-shell crab is caught either in traps, like those 

 used for lobsters, or on lines baited with stale meat, the entrails of 

 fowls, etc. No hook is used in "crabbing;" the crabber simply sup- 

 plies himself with the necessary bait, with a dip-net and with a quantity 

 of cheap twine. The twine is cut into suitable lengths and is tied 

 to pieces of bait and the latter hung into the water from the side of 

 the boat or dock, or at intervals along a long "trot line. " The fisher- 

 man goes from string to string and pulls each up slowly until the bait 

 is near the surface of the water, when, with a quick dip of the net, 

 he captures the crab or crabs that may be clinging to the meat with 



