36 PRACTICAL ZOOLOGY. 



THE SOW-BUG. 



Sow-bugs are usually to be found under boards and 

 stones, and in other damp places. Get the largest speci- 

 mens for this study. 



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



2. Find and describe the eyes. 



3. What are the peculiarities of the antennae ? 



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 grass- 

 hopper. 



Where is the line of division between the head and 

 thorax? Count the appendages which may be sup- 

 posed 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 ? 



6. How many segments are there in the abdomen ? 



7. How many pairs of legs are there ? How many seg- 

 ments has each leg? Do the legs all extend in the 

 same direction ? 



8 A series of thin, over-lapping 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 



