CHAPTER VII 

 CRUSTACEANS 



Crawfish 



Suggestions. — In regions where Crayfish are not found, alive 

 crab may be used. Locomotion and behaviour may be studied by 

 providing a tub of water, or better, a large glass jar such as a 

 broad candy jar. For suggestions on study of internal structure, 

 see p. 58. 



Habitat. - Do you often see crawfish, or crayfish, mov- 

 ing about, even in water where they are known to be abun- 

 dant? What does your answer suggest as to the time 

 when they are probably most active ? 



Why do you never see one building its chimney, even 



where crayfish holes are abundant? Is the chimney 

 always of the same colour as the surface soil? Are the 

 crayfish holes only of use for protection? In what kind 

 of spots are crayfish always dug; Why? What 

 becomes of crayfish when the pond or the creek dries up ? 

 How deep are the holes ? How large are the lumps of 

 mud of which the chimney is built? How does it get 

 them out of the hole ? Why is the mud built into a chim- 

 ney instead of thrown away ? (What would happen to a 

 well with its mouth no higher than the ground?) Why 

 are crayfish scarce in rocky regions ? 



How does the colour of the crayfish compare with its 

 surroundings? Is its colour suited to live in clear or jnuddy 

 water? Define protective colouration. 



