142 ARTHROPOD A. 



If you will walk along a beach some quiet night with a lan- 

 tern you will probably see something of the night activities of 

 these animals. 



1. Select a large specimen and count the number of segments. 

 Is the body divisible into head, thorax, and abdomen? 



2. The eyes are not stalked. Are they compound? 



3. The second antennce of the male are very large. Compare 

 them with the first antennae and with the antennae of a female. 



4. Around the mouth are the labrum, forming an upper lip, 

 the first maxillipeds (fused), forming a lower lip, and between 

 them the mandibles, first maxillce, and second maxillce. 



5. Examine the appendages behind the mouth. How many 

 are there? How many bear claws? Compare these claws with 

 those of a lobster, and see how they differ. Which appendages 

 are used in crawling ? Why are some of the appendages arranged 

 so they can be twisted around by the sides of the animal ? What 

 are the remaining appendages used for? Watch an animal jump. 



6. Spread the appendages apart and find the gills, which are 

 attached to the bases of the appendages. 



Make a drawing of the animal. 



PORCELLIO OR ONISCUS. (Sow-Bug.) 



These animals occur in damp places, such as under stones, 

 logs, etc., and in cellars. They live for the most part on decaying 

 vegetable matter. To what class of the Arthropoda do they be- 

 long? 



1. Notice the shape. Is this an adaptation? 



2. Is the body divisible into head, thorax, and abdomen? 

 Count the number of segments. Is there any evidence of fusion 

 at the posterior end of the body ? 



3. Examine the appendages. 



(a) Are the eyes stalked or sessile? 



(b) Only one pair of antenna) is present, the first pair being 

 rudimentary. 



(c) The mouth appendages are small. They consist of man- 

 dibles, two pairs of maxillce, and one pair of maxillipeds. 



