THE ARMATURE OF ORBWEBS : VISCID SPIRALS. 83 



whifli she lias carried around witli her. This makes one section or string 

 of her beaded spiral. The next string, C-D-E, is comjileted in the same 

 way, the general course being in the direction of the arrows. 

 Snider ^'^^ ^'^^ space between the newly made viscid spirals (as A) 

 and the next occurring foundation spiral (SFx) is diminished, 

 the spide'r does not need to walk along the intervening radii, IR, 2R, etc. 

 The distance between the spiral foundation and the new points of opera- 

 tion is then short enough to allow her to grasp the former with her fore 

 feet; and thus she strides along, oscillating between the viscid spirals and 

 the foundation spiral, and between the two radii separating the beaded 

 string which she is weaving in. Very often, indeed, there is no need to 

 walk along the radius at all, but from the beginning to the end the 

 spider is able to accomplish her work by the simple process of reaching 

 to the spiral scaffold. In that case, of course, the dotted line and arrows 

 of Fig. 81 only represent in a general way the course of the body. 



In ascending the orb, as well as in crossing from one side to another, 

 the arancad must plod through all the course which has thus been imper- 

 fectly indicated ; but when she is on the downward course she 

 is not compelled to stride along the radii and spiral scaffolding, 

 and therefore simply drops from the point of attachment last made to the 

 next radius. (Fig. 82.) This sheer descent of her web is made when those 

 radii are reached which cross from the centre laterally to the circumfer- 

 ence, when it is manifest (see Rl, R2) that all required is that she should 

 drop from the radius last intersected (R2) to the one next in order (R3). 

 This is the usual course of the spider, and not until she makes the turn 

 and again proceeds laterally across her orb is she required to renew the 

 more tedious process described. 



It is obvious that those (Jrljweavers which make vertical webs must, 

 from necessity of the case, vary their mode of proceeding while spinning 

 the spiral lines, according to the position which they may chance 

 ,, "^P"^ at the time to have upon their orbs. This fact may be illus- 

 trated at Fig. 83, which represents diagramatically the progress 

 of the spider around an entire concentric. The web is represented with the 

 radii, R, R, in place, and the spiral scaffold, S, located. The spider had 

 already begun upon the viscid spirals, and had laid in one circular course 

 of the series. Let us suppose that she starts at the point x on radius marked 

 Rl, to lay in her second spiral concentric. The ordinary course would be 

 to stride along the radius to the spiral scaffolding (S) and so to the point 

 x2, where she would fa.sten her new string. But it is obvious that such a 

 course would be wasted time and energy, and that her purjiose would be 

 accomplished more readily by dropping directly from x on Rl to R2, and 

 carrying her line to the point of junction x on the last named radius. This 

 is precisely what the spider does, and this is her habitual method on all 

 parts of her orb where such a direct drop is practicable. 



