EPEIRA. 181 



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 chelicerce or mandibles. Notice their structure and 

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

 at the tip of this claw. 



(6) 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 seg- 

 ments 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 func- 

 tion 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-sacs 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. 

 Montgomery: Studies on the Habits of Spiders, Particularly Those of the 



Mating Period. Proc. Acad. Nat. Sci., Philadelphia, 1903. 

 : On the Spinnerets, Cribellum, Colulus, Trachea? and Lung-books of 



Araneads. Proc. Acad. Nat. Sci., -Philadelphia, 1909. 

 : The Development of Theridium, an Aranead, up to the Stage of 



Reversion. Jour. Morph., 20, 1909. 



The Significance of the Courtship and Secondary Sexual Characters 



of Araneads. Am. Nat., 44, 1910 

 Peckham: Observations on Sexual Selection in Spiders of the Family At- 



tidae. Occas. Papers Nat. Hist. Soc, Wisconsin, 1 and 2. 

 Wood: Autotomy in Arachnida. Jour. Morph., vol. 42, No. 1, 1926. 



