CHAPTER V 

 CRAYFISHES AND THEIR RELATIVES 



112. A study of the crayfish. Laboratory study. 



A.. Regions. The body of the crayfish has two distinct 

 regions. The dorsal surface and sides of the 

 anterior region are covered by a cape, consist- 

 ing of a single piece of shell-like material. This 

 region is the cephalothorax (from Greek = 

 head-thorax) . The posterior 1 region is the 

 abdomen. 



1. Which region is composed of a number of similar 



segments ? 



2. Which region has the legs, antennae (feelers), and 



eyes attached to it? 



B. Adaptations for walking. ; 



Place a crayfish in the center of a pan witfi 

 enough water to cover the animal. If the cray- 

 fish does not walk, touch it with the pincers. 



1. How many pairs of legs are used in walking? 



2. In what directions (forward, backward, or sideways) 



are you able to get the crayfish to walk ? 



3. State whether or not the " large claws " are used in 



walking. 



4. Are the walking legs composed of one piece or of 



several movable parts? Of what advantage 

 is this to the animal ? 



5. (Optional.) Make a sketch ( x2) of one of the legs to shovi 



its structure. 



1 The meaning of each of these terms is explained in 6. 

 151 



