176 ARTHROPODA. 



convenient places for observation, the construction of new webs 

 may be observed. Notice how the framework of a round web is 

 laid and then how the threads are attached to the famework. 

 Are any of the legs used in handling the thread? Are spiders 

 equally active at all times of the day? 



Spiders' webs may frequently be seen floating in the air, 

 especially in the late summer or autumn. By watching spiders 

 that are on fences and bushes the formation of these threads 

 may be observed. Watch such a spider and see if you can deter- 

 mine the use to which the thread is put. 



Capture a spider and watch it descend by a thread. Where 

 is the thread formed? Does the spider hold to it with its legs? 

 Keep taking the thread up so that the spider cannot reach the 

 ground, and see if there is a limit to the amount that can be 

 formed. When the spider starts to climb the thread see how 

 this is done, and whether the thread is taken up as the animal 

 climbs or is allowed to float free. 



Find where spiders lay their eggs. Some carry them. If 

 you can find a specimen with an egg-sac, see how it is carried 

 and whether it will drop its eggs when frightened. Remove the 

 egg-sac and see if the spider will accept it again. Open 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 appen- 

 dages used sometimes for locomotion and sometimes for feel- 

 ing? 



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 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. 



