88 AMICKICAN Sl'IDEKS AND THEIR SPINNINGWDltK. 



iiTC'<;ular forms. To the naked eye or under a eonnnon hand glass the 

 beads often show as quite regularly arranged globules of two or three 

 sizes. (Fig. 85.) 



These two opinions ai'e very deeply seated in the popular mind : tirst, 



tiiat spiders are able to shoot out from their spinnerets lines or rays; 



second, that they are able to retract within the abdomen the lines 



Elasticity „•] ,;,.]( t]i(.y spin. In the former case the delicate filaments are 



oi bpn-al ^,j^.^^.^^^,^| from the spinning tubes as liquid silk, but the movement 



of the air is the means by which they are borne swiftly aloft or 



outward from tlie spinnerets. There is no ground in fact for the latter 



opinion, although it is not strange that casual observers should be deceived, 



as the optical illusion, for such it is, is very complete. The illusion is 



occasioned by two causes: the first is the action of the spider which in 



ascending a dropped line, for example, gathers up the thread under her 



-...o<>«<.»o<,<,<.»-,<>.,«>,«>„o.-^„ jaws, as she goes, in a little flossy ball so delicate 



as to escape ordinary observation. The other cause 



is the extreme elasticity of the line, which may be 



-.-oooo««j„oo-»,>o.^..<>«^ extended greatly by the application of a slight force, 

 ■°°~*^'^~**"''^"''>*"^°- and on its removal will contract projiortionately. 



^><«>~Kx«o.MK><^~ ^iie who has carefully watched the movements of 



.<«x~o-.,^»»o<«- Orbweavers while laying in their spirals must have 



observed, wdiat Blackwall has already noted, ^ that in 

 -^®^«'®*«<*»o««*«»o-<»- passing from one radius to another the viscid line 

 .,,aK^^,<sy,^^^^^^^'^^^^i is usually drawn out to a much greater extent than 

 viG. 8.5. Appearance of beads IS iicccssary to coiiuect the two. Taking the last 

 to the eye. Spiral cross line, after its formation, Fig. 80, iii — iii 



j)rolonged, as the base of a triangle, the line is actually drawn out before 

 it becomes taut and is fastened as at iii — x, ab, occuiwing thus two sides 

 of the triangle. I have seen the line thus stretched until it certainly was 

 nearly if not quite twice the length finally assumed. This elasticity is of 

 course of immense advantage in the preservation of tlie snare under the 

 struggles of vigorous insects entrapped within it, as well as before the vio- 

 lence of wind, and beneath the weight of dew and rain. One may easily 

 assure himself of this elasticity by touching some object to a single viscid 

 string and drawing it out until it snaps. lie will find that the united 

 length of the two lines thus expanded will often be as much as four, six, 

 or even eight times the length of the original line. 



But there results from this elasticity another advantage which 1 bi-lieve 



has not heretofore been noted. It presents in part an explana- 



Forma- ^jqj^ q£ ^^j-^^ formation of the beads, a point which has been 



Beads nmch discussed and never yet fully explained. The spiral line as 



emitted from the spinnerets is covered with the viscid matter 



of \vliicli the beads are composed uniformly distributed over its surface. 



' Spiders of Great Britain and In^land, Intr., paju'c 10. 



