THE GENESIS OF SNARES. 



345 



nearly approaches, in the habitual form of its snare, that form which, as 

 I have shown, incidentally results from the long use of Theridium's web 

 of intersecting lines. 



The step is not a large one by which we may conceive the snare just 



described to be transformed into that of the dome shaped web of Linyphia 



marginata, or the bowl shaped web of Linyphia communis. It 



From only needs, in the former case, a little more downward pressure 



upon the cords at the edges, and in the latter a little more 

 Dome. 



pressure upon the marginal cords upward, to complete the proc- 



ess. i Fig. 335.) We may now pass from Lineweavers to Tubeweavers. A 



glance at the snare of Agalena noevia, for example, as represented in 



Fig. 215, page 217, and Fig. 336, will show how close is the resemblance 



between it and the snares of Linyphia already described. Agalena has a 



sheeted web of open spinningwork, or of close, irregular meshwork, as one 



may choose to put it, whose weft becomes 



much thickened in course of time by fre- 



quent overlaying. It also has the crossed 



lines extending upward, for the most part, 



but often downward also, representing the 



original rude intersecting lines of our sup- 



posed primitive snare. This retitelarian fea- 



ture of the web is a most important factor 



in the daily capture of prey, by signaling 



their presence to the waiting proprietor; 



by arresting and trapping them so that they 



fall upon the sheeted premises beneath ; and 



by actually entangling them. 



This niOSt highlv Organized Of all the 

 , . 



lubeweavmg species has therefore substan- 

 tially a Lineweavers snare. To this structure is added the tube, which, 

 in point of fact, is not the snare, but the nesting place. I have already 

 shown, in the chapter on Nesting Habits (Chapter XVII.) , the manner in 

 which this feature of the snare may have been gradually developed by 

 the natural action of the spider. In point of fact, the tube is the typical 

 nest of all species, and is naturally formed by the movements of the spider 

 within a limited space, spinning out as it moves the silken material which 

 it secretes. 



Theridium, and still more habitually and definitely Linyphia, will form 

 a little tube like structure by the mere gravity of the body as it hangs 



upon its snare in this manner: The eight legs reach upward, 

 From forming what may be called the sectional outline of a tube cut 

 ,p, horizontally. The weight of the spider, aided by the violent agi- 



tation of its snare when struck by an insect, pulls down these 

 eight points in such a way that a little conical or dome like tent is formed 



Sheeted web and tube of Agalena 

 ncevia, woven on a hedge. 



