EPEIRA 



197 



several egg sacs and see if the eggs all appear to be in the 

 same stage of development. 



Study the movements of the animal and see how many of 

 the appendages are used in locomotion. Are any of the ap- 

 pendages used sometimes for locomotion and sometimes for 



feeling? 



Examine the external structure of Epeira. 



1. Into what parts is the body divided? Do both parts 

 bear appendages? 



2. Look for eyes on the anterior end of the body. How 

 many are there? Do they seem to be simple or compound? 

 Determine whether a specimen can see. 



3. The following appendages should be found: 



(a) The chelicerae or mandibles. Notice their structure 

 and see that each ends in a sharp claw. The poison gland dis- 

 charges at the tip of this claw. 



(b) The pedipalpi or palpi. How many segments have 

 they? Examine their tips for claws. What are they appar- 

 ently used for? 



(c) Four pairs of legs. Are they all alike? Count the 

 segments and examine their tips for claws. 



(d) On the abdomen, three pairs of spinnerets. Notice 

 their positions and see if they are segmented. Understand 

 their function and whether they are all used at the same 

 time. They are probably true abdominal appendages. 



4. On the lower surface of the abdomen, near its anterior 

 end, are two slits, the openings into the lung sac or lung 

 books. They are respiratory in function. 



5. Just in front of the spinnerets is a minute median pore, 

 the spiracle, that is often very hard to find. It is the external 

 opening of a series of abdominal tracheae. 



Make a drawing of a ventral view. 



Baerg: The Black Widow; Its Life History and the Effects of the 



Poison. Sci. Mo., vol. 17, 1923. 

 Comstock: The Spider Book, 1913. 

 Emerton: New England Spiders. Trans. Conn. Acad. Many papers, 



1882-1915. 



