SILK SPINNING AND HANDIWORK 55 



The viscid or entangling webs of the orb weavers and certain 



other spiders 

 The viscid ball and pendulum line of Mastophora, Dichrostichus, 



and Cladomelea 

 The viscid hackled band in the diverse capturing webs of the 



cribellate spiders 



The catching thread of Miagrammopes 

 The retiarius of the Dinopidae 



Bands for Binding the Prey 



The swathing band of the orb weavers 



The swathing film of the comb-footed spiders 



The swathing band of Hyptiotes 



The entangling ribbon of the Hersiliidae 



The capturing band of Drassodes and other vagrant species 



The above requirements and others not listed are met by the 

 production of different kinds of silk, which are used, seemingly at 

 the will of the spider, either separately or in combination to pro- 

 vide the special threads, desired bands, or drops for a particular 

 project. 



THE SILK 



The silk of spiders is a scleroprotein which is produced as a 

 liquid in varied and voluminous abdominal glands. When drawn 

 out of the spinnerets, the liquid ordinarily hardens to form the 

 familiar silken threads. It is believed that the mechanical stretching 

 of the silk during the drawing of the lines is responsible for the 

 hardening, rather than exposure to air or any chemical process. 

 Viscid silk is produced in some of the glands and remains sticky 

 for long periods. An analysis of the silk has shown that it is a com- 

 plex albuminoid protein quite similar to that produced by the silk- 

 worm, although this similarity is denied by some investigators. The 

 silk of the silkworm comes from modified salivary glands located 

 in the head, whereas that of the spider is derived from transformed 

 coxal glands in the abdomen. 



Spider silk is noted for its strength and elasticity. The tension 

 necessary to bring a compound thread .01 cm. in diameter to the 

 breaking point was once found to be eighty grams. This consid- 

 erable tensile strength, which is said to be second only to fused 



