BUTHUS. EPEIRA. 175 



BUTHUS. (Scorpion.) 



Living specimens of these animals are not usually available 

 for laboratory study, They live for the most part concealed 

 during the day under old bark and in crevices and holes and are 

 active at night. Their food is largely spiders and insects which 

 are seized by the claws and killed with the abdominal sting. 



1. Into what parts is the body divided? How many seg- 

 ments are recognizable? Which are the most freely movable? 



2. Look for eyes. Do you find any besides the large pair? 



3. Find four pairs of slit-like openings on the ventral side of 

 the pre-abdomen. These are the stigmata, the openings of the 

 lung-books. 



4. Find the following appendages: 



(a) The chelicerce. What is their structure and where are 

 they placed? 



(b) The pedipalpi. Compare them with the chelicerae and 

 count their segments. 



(c) Four pairs of walking legs. Count their segments and see 

 if they are armed with claws. 



(d) The comb-shaped pectines. Are they on the thorax or 

 the abdomen? Their function is doubtful. 



5. Examine the mouth. Are there any jaws? Is a labrum 

 present ? 



6. Find the position of the anus. The terminal spine is pro- 

 vided with a poison gland and serves as a sting. In the living 

 animal, the post-abdomen is habitually carried over the back. 



Make a drawing of the under side of a specimen. 



EPEIRA. (Round-Web Spider.) 



Examine the webs of different species of spiders and see how 

 they are constructed. Do all of the webs have places for the 

 concealment of the owners? Do all spiders seem to construct 

 definite webs for the capture of insects? How do spiders entan- 

 gle insects in their webs? Do different kinds use different 

 methods? What parts of insects are eaten? 



By destroying webs that are occupied by spiders that are in 



