The Life of Spiders 



The stabilimentum is sometimes an elaborate structure. This 

 is especially true in the webs of the young of Metargiope trifas- 

 ciata (Fig. 193). In fact 1 have observed that immature spiders 

 are more apt to make a stabilimentum than old ones. I have 

 noted this especially with Metargiope and with Uloborus. The spi- 

 ders of the genus Cyclosa make a stabilimentum composed largely 

 the dry skins of their victims. 



The trapline. — When the orb is completed, many orb- 

 weavers rest on the hub and wait there for their prey; if disturbed 



they either drop to the 

 ground, spinning a drag- 

 line as they go, up which 

 they ascend to the web 

 later, or they rush off at 

 one side to the support of 

 the web. In many other 

 species the spider has a 

 tent above or at one side 

 of the orb to which it 

 retreats when disturbed 

 and in which it waits for 

 the ensnarement of its 

 prey. This retreat is con- 

 nected with the hub of the 

 web by one or more 

 threads which serve as 

 a means of passage to and 

 from the web. When wait- 

 ing for its prey, the spider 

 rests in the retreat with 

 one or more of its feet 

 upon the line leading to the hub of the orb; by this means it 

 can feel any disturbance of the web. This use of the thread 

 connecting the retreat with the orb has suggested the name 

 trapline for it. 



The tracks of orb-weavers. — In running about on their orbs, 

 spiders ordinarily use the radii as means of support; and in passing 

 to and from their retreat, they use the trapline, avoiding, if 

 possible, contact with the viscid spiral line. But it sometimes 

 happens, especially if a spider be frightened, that the orb is 



Fig. IQ3. STABILIMENTUM OF METARGIOPE 



204 



