Superfamily Argiopoidea 



metatarsi are much curved and are armed below with a series 

 of spines (Fig. 255); the calamistrum occupies more than half 

 of the length of the segment. 



I have studied the hackled band of our two genera, Uloborus 

 and Hyptiotes. The structure of it is the same in the two and is 

 quite characteristic (Fig. 236). There is a warp consisting of two 

 straight threads, upon which the woof of viscid silk is borne. 

 The two strands of the warp are strictly parallel, are smooth, 

 and are exceedingly delicate. They do not show well in the figure 

 as they were out of focus when the picture was taken. 1 found, 

 with the high magnification required, that it was impossible 

 to get both the warp and the woof in focus at once, they being 

 in slightly different planes, the woof resting upon the warp. 

 I he woof consists of an exceedingly regular series of overlapping 

 lobes. 



It seems probable that the warp is spun from two spigots, 

 one on each of a pair of spinnerets, and that the woof is combed 

 from the cribellum by the calamistrum. 



Our two genera can be separated as follows: 



TABLE OF GENERA OF THE ULOBORID/E 



A. Cephalothorax ovate, rounded behind. Uloborus 



AA. Cephalothorax wide in the middle, narrowed in front and 



cut off squarely behind; the sides concave in front, nearly 



parallel behind. Hyptiotes 



Genus ULOBORUS (U-lob'o-rus) 



The great length and robust form of the front legs of these 

 spiders cause them to present a very characteristic appearance: 

 this is shown in Fig. 257, which represents our most common 

 species. Other species differ in the form of the abdomen, in the 

 arrangement of the eyes, in markings, and in the nature of the 

 clothing of hairs. Figure 238 represents the ventral aspect of 

 the cephalothorax of Uloborus americanus. 



The spiders of this genus make orb-webs, which resemble in 

 general appearance those of the more common orb-weavers, the 

 Argiopidre, but differ in that the spiral thread is a hackled band. 

 These webs are almost always horizontal, and usually made in 

 low bushes, or between objects near the ground, or in buildings, 



2() 3 



