CRUSTACEA 



298 



protect these crabs by making closed seasons and by specifying size 

 limits, but the natural history of this species has not been adequately 

 studied. 



Crawfish Astacus (Pacific) ; Cambarus (Atlantic). Many species of 

 lliese two genera inhabit North American fresh waters and lowlands, 

 several of them growing to 6 inches in length. They are extensively 

 used for food in Europe and are growing in favor in some parts of this 

 < ountry. The flesh is delicate and sweet, like that of lobsters and crabs, 

 stud there is no good reason why they should not be much more widely 



FTG. 136. Female and male crawfish, the female with eggs 



appreciated and utilized. In the waters they often form the chief food 

 of our game fishes, especially of the black bass. 



. Crawfish are found in the fresh waters of the temperate zones of all 

 the continents except Africa, and it is evident that they have developed 

 from a number of different marine forms. The largest crawfish in 

 the world is Astacopsis frankli&ii, found in the small streams along 

 the north and west coasts of Tasmania. These often weigh as much 

 as 9 pounds ; and if they could be safely introduced, they might give 

 us an industry for our fresh waters that would rival lobster culture. 



The land crawfishes, known as " chimney builders," dig holes in soft 

 ground, generally down to water. These are about an inch in diameter 

 and are surrounded by a chimney of excavated earth. This burrowing 

 habit makes them serious pests in embankments and levees. They are 

 also, in part, vegetable feeders and are often destructive to young plants 

 of field or garden. A few drops of carbon bisulphide in a burrow will 



