The Life of Spiders 



spinning tubes of this pair of spinnerets and is therefore the prod- 

 uct of the pyriform glands. The spiders that I have seen make 

 attachment disks were Aranea frondosa and a species of Amau- 

 robius. 



The following interesting observation was reported to me by 

 Prof. Cyrus R. Crosby: — "The other day when attempting 

 to capture an Aranea trifolia she attached her thread but had 

 no time to change to the dragline and so spun a band of silk a foot 

 long before she was able to make a new attachment and start the 

 dragline." 



The swathing band. — The band of silk with which the orb- 

 weaving spiders envelop their prey may be termed the swathing 

 band. The method of making this band is described on an earlier 

 page. I have watched the process many times, but owing to the 

 timidity of the spiders observed, I have never been able to deter- 

 mine to my complete satisfaction whether the silk comes from 

 all of the spinnerets or only from the hind and middle ones. It 

 is easily seen that the band is composed of a great number of fine 

 threads and it appears to come from all of the spinnerets. If 

 this is true, it is the product of both the pyriform and the acini- 

 form glands. I have observed the making of the swathing band 

 only by orb-weaving spiders; probably other spiders have similar 

 habits. 



The swathing film. — Spiders of the family Theridiidae use 

 in swathing their prey a film of silk which differs from the swathing 

 band of the orb-weavers. This silk is emitted from two or four 

 spigots, one or two as the case may be, on each of the hind spin- 

 nerets. These spigots are the outlets of the lobed glands; which 

 have been found only in this family. 



The viscid thread. — In the webs of orb-weaving spiders there 

 occurs a peculiar viscid thread; this is the spiral line forming 

 the larger part of the orb. If this line be touched, ever so lightly, 

 it will adhere to the object touching it, and when this object is 

 removed the line will stretch greatly. This is the trapping por- 

 tion of the web; the viscid nature of the silk causes it to adhere 

 to an insect touching it; and the elasticity of the thread prevents 

 the insect from breaking it at once and allows the insect to become 

 entangled in other turns of the spiral; in this way the prevention 

 of the escape of the insect is assured if the victim be not too 

 powerful. 



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