THE ARMATURE OF ORBWEBS : VISCID SPIRALS. 



81 



s-s 



FIG. 79. Clamping a spiral string. 



which the spider all the while has been rapidly approaching, and grasps 

 it with the claws just beneath the point where the new string will cross. 

 This then is the attitude of the spider at this point of her operations. 

 Fig. 79. One hind foot (4.o) grasps the radius near and below the point 

 (xxi just opposite the last point of 

 attachment. The other 

 Paying ^ind j eg (4 j) j s rea ched 



V" , e out beyond and above the 

 spider's abdomen, hold- 

 ing the new string (ns) so that the 

 two parts form an angle. Now the 

 abdomen drops towards the radius. 

 The raised foot lets go the stretched 

 string at the very moment that the 

 spinning fingers grasp the radius 

 (at xx) and clamp the string there- 

 to. The string being released at 

 the same moment, contracts with 

 a sudden snap, and thus forms the 

 little iiiterradial or portion of the 

 spiral line between the two radii. Fig. 80 shows the first action in this 

 process. The strings I I, II II, are sections of a finished spiral line, and 

 III x III is a string in the act of being spun. The line x is caught up 

 by the claw, cl, upon a tarsal spine, ts, (apparently) or a metatarsal spine, 

 ms, and pulled out from the abdomen to which it is attached by ab. The 



foot (here greatly exaggerated) moves rap- 

 idly towards ab, and the line is fastened at 

 the point III, indicated on the right hand 

 radius, r. The large tarsal spines which arm 

 the terminus of the tarsus of Argiope coph- 

 inaria are continually used by that species 

 to hold the beaded string as it is thus 

 drawn out. In the meantime, of course, 

 the remaining limbs of the spider have 

 been carrying her forward. The 

 legs on the side towards the ceii- 

 p^ tre of the hub reach upward and 



grasp the spiral scaffold (ss) if 

 the scaffold happens to be within reach. 

 This is frequently the case during the 

 whole process of spinning; but frequently also during the placing in of 

 the first spiral strings included between two scaffold lines the spider is 

 unable to reach so far, and therefore must go around the radius, as will 

 be described presently. The legs on the side of the body towards the 



FIG. 80. Drawing out a beaded spiral. The 

 leg much exaggerated. 



