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 
see only needs, in the former case, a little more downward pressure 
ene $ upon the cords at the edges, and in the latter a little more 
pressure upon the marginal cords upward, to complete the proc- 
ess. (Fig. 335.) We may now pass from Lineweavers to Tubeweavers. A 
glance at the snare of Agalena nevia, 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 most highly organized of all the F's-336. Sheeted web and tube of Agalena 
Tubeweaving species has therefore substan- ee 
tially a Lineweayer’s 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, 
ea ae forming what may be called the sectional outline of a tube cut 
Tube. 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 
