THE PEATHERFOOT SPIDER, ULOBORUS PLUMIPES. 



177 



the centre ; in the structure of the hub ; in the preliminary spiral scaffold ; 



in the central concentrics, which correspond with the notched zone; in 



the form and distribution of the spirals; in the character of the 



• ^^1, rib'JO" decorations; in the manner in which the snare is swuns: 

 ume Orb- .rii-i--i •• , 



weaver. rouutlation hues ni whatever site it may be placed ; in the 



position of the spider underneath the web ; — in all these points 

 the spimiingwork of Uloborus is analogous to that of Orbweavers, espe- 

 cially Tetragnatha, or of the Orchard and Hunchback spiders. 



There is, however, one important difference. The spiral concentrics, in- 

 stead of being composed of single lines covered with viscid beads, as in 

 ^ . typical snares of the Orbitelarite, are composed for the most part 



Beads ^^ several very delicate filaments, although in certain parts the 

 thread is single. To threads and filaments alike are often at- 

 tached a number of minute objects, opaque, and for the most part amor- 

 phous; but many of them being very small globes of a yellow color, per- 



Fici. 164. Circular ribboned decorations on the snare of Uloborus. 



haps the pollen of flowers. They adhere to the single threads, but more 

 fully to the portions containing several distinct filamenis. These opaque 

 objects have so much the appearance of beads that a careless observer is 

 likely to be deceived by them; at least, I was thus led astray in my first 

 studies of the Uloborus snare. There are, however, no viscid beads upon 

 any of the lines, although the thread is certainly very adhesive, chiefly 

 I suppose by reason of the delicacy and flocculence of the fibre. The 

 smooth point of a pencil touched to it does not adhere; but when my 

 finger was laid ujion a spiral it adhered as in the case of a beaded web. 

 In this respect the snare of Uloborus resembles that of the Triangle 



spider, Hyptiotes cavatus, and also certain species of the Clubion- 

 Relations ijgg^ g^^j^jj ^^ Dictyna philoteichus and other species of that genus, 

 culent '^^"^ flocculent web was discovered and described by Blackwall, 

 Spirals. ^^^^^ i*^ produced by special organs known as the cribellum and 



calamistrum. The calamistrum is located upon the metatarsus 

 of the hind paii-s of legs. It resembles somewhat in form the flyers upon 



