Crustacea. 45 



1 6. Why should the name Crustacea be applied to such animals 

 as the crayfish ? 



Read The Crayfish, Huxley. 



Topics for Reports. The Lobster Industry. Shrimps. Crabs, 

 [ermit Crabs. Sea Spiders. Fiddler Crabs. Cocoanut Crabs. 



THE SOW BUG. 



Sow bugs are usually to be found under boards and stones, and 

 other damp places. Get the largest specimens for this study. 



1. The first part is the head, or carapace. 



2. Find and describe the eye.s. 



3. What are the peculiarities of the antennae? How many? 



4. The jaws and maxillae are closely pressed together, forming 

 a short, blunt projection under the head. The tip of this blunt 

 proboscis is usually black. A longitudinal groove shows the line 

 of union of the hinder maxillae. By pinching the body of a live 

 sow bug, the mouth is sometimes more clearly shown by the 

 exudation of a liquid, as in the case of a grasshopper. 



Where is the line of division between the head and thorax? 

 Count the appendages which may be supposed to belong to the 

 head ; how many rings do these indicate? 



5. The line of division between the thorax and abdomen is 

 indicated by an abrupt change in the size of the segments. How 

 many segments has the thorax? Compare the numbers of seg- 

 ments in thorax and abdomen with those of the crayfish. 



6. How many segments are there in the abdomen ? 



7. How many pairs of legs are there? How many segments 

 has each leg? Do the legs all extend in the same direction? 



8. A series of thin, overlapping plates under the abdomen are 

 the gills. In the anterior plates observe the white air chambers. 

 Beginning at the foremost of these gills, pick them apart with a 

 needle. Remove them, and with a lens make out their shape and 

 arrangement. 



9. Under the thorax of the female there is a series of thin 

 membranes attached near the bases of the legs. These are the 



