CRAYFISH, LOBSTERS, SPIDERS, AND INSECTS 141 



from their burrows. One claw of the male is much larger 

 than the other. When these crabs are disturbed, their 

 claws are brandished ia an amusing manner, strikingly 

 suggestive of the motions of a viohnist, whence these forms 

 have received the common name of fiddler crabs. 



Sow bugs. — These are dark-colored, oval-bodied animals 

 with several legs, that live beneath old boards, chunks of 

 wood, stones, etc. They are known as sow bugs (Fig. 81), 

 and wood lice, and feed largely 

 upon vegetable matter, especial- 

 ly upon that which is offensive 

 to man. Some closely related 

 crustaceans, found in the same 

 situations as the sow bugs, can 

 roll themselves up into a ball, 

 and so are called pill bugs. 



Regeneration of lost parts. — 

 Like the crayfish, other crus- 

 taceans are able to reproduce 



lost parts. A lobster's claw Fig- si. -Sow bug. Enlarged. 



usually breaks off at a certain point, the "breaking joint," 

 and in the course of succeeding molts will be gradually 

 reproduced. It is thought by some that this is a means of 

 protection, for this breaking adaptation is confined to those 

 appendages which are most apt to be seized, namely, the 

 five thoracic legs. The antennae of a lobster will also be 

 renewed if broken off. Regeneration takes place in the 

 walking legs of shrimps, crayfish, hermit crabs, etc. 



Commensalism. — A certain sea anemone (Adamsia) is 

 sometimes found attached to the shell of the hermit crab. 

 In this position the sea anemone is carried about, and is 

 thus enabled to obtain a more varied and abundant food 



