The Life of Spiders 



insects that visit them, resembling in this respect the ambush-bugs; 

 and many of the mining spiders lie in ambush at the entrance 

 of their burrows, ar.d spring forth to seize insects that come near. 



The net-building spiders. — The great majority of sedentary 

 spiders, as those that do not wander in search of prey are termed, 

 spin webs or snares for the trapping of insects, and wait either 

 upon or near the webs where they can easily rush upon an en- 

 tangled insect. 



The commensal spiders. — Excellent examples of feeding at 

 the same table with other species, or commensalism as it is termed, 

 is exhibited by species of the genus Argyrodes. These small 

 spiders live in the snares of larger web-building species and feed 

 upon the smaller entrapped insects that are neglected by the owner 

 of the web. 



Means of destroying the prey. — Spiders destroy their prey by 

 means of venom secreted by a pair of glands in the cephalothorax; 

 the ducts from these glands open, one on each side, through a 

 minute pore near the tip of the claw of the chelicera. 



Most of the web-building species swathe their victims in a 

 sheet of silk. The act of swathing can be easily observed by 

 throwing a large insect into the web of a Miranda. 1 he spider 

 first rushes at the insect and pierces it with the claws of its cheli- 

 cerae, and then darts back into a position of safety; this may be 

 repeated several times; or, if the spider is not afraid of its victim, 

 the biting may be omitted. Then the spider approaches the 

 insect and pulling out a sheet of silk from its spinnerets with one 

 hind leg thrusts the sheet against the insect. In doing this the 

 spider uses first one hind leg and then the other. In the case of 

 a large Miranda this sheet of silk is sometimes an inch in length, 

 the body of the spider being held that far from the insect; under 

 these conditions the sheet can be seen to be composed of a very 

 large number of parallel threads, probably a thread from each 

 of the small spinning tubes of all the spinnerets enters into the 

 composition of the sheet. As soon as the sheet is fastened to 

 the insect the spider rolls the insect over and over and thus wraps 

 it in its shroud. 



V.— THE SILK OF SPIDERS 



The silk glands have been described in the chapter on internal 

 anatomy; and the spinning organs, in the one on external anatomy; 



187 



