HORIZONTAL SNARES AND DOMED ORBS. 167 
three common variations of the form: First, a plain sheet of thin silk 
attached to the under part of leaves or suspended between branches as in 
_the webs of Linyphia costata. Second, the snare of L. communis, represented 
at Fig. 156. It has a mass of right lines, r, to which is suspended a bowl 
like sheet, b, beneath which again is a dish shaped sheet, d, of more open 
spinningwork with the concavity upward, as in the bowl. The snare from 
which this figure was drawn had a total height of from twelve to fourteen 
inches. The diameter of the bowl was from 
six to seven inches, its depth one and a half 
to two inches. ; 
Linyphia communis hangs inverted to the 
lower surface of her bowl, and is thus pro- 
tected from assaults by the underlying floor 
or dish or curtain, d. | 
A third variation is that of the beautiful 
snare of Linyphia marginata (L. marmorata 
of Hentz), which is in form precisely like 
that just described except that the bowl 
becomes therein a dome, That is to say, } 
the sheet, b, has the concavity downward _/ 
instead of upward, and the dish or cur- / ‘S J 
tain undergoes a similar change. In [2 
other words, the web of Marginata AGE 
has the exact form of Basilica’s Ve 
web, except that in the latter the 
dome, d (Fig. 154), is constructed 
of open regular meshes formed by 
the intersection of radiating ribs 
of silk with notched concentrics, 
while Marginata’s dome is woven 
of irregularly placed threads into 
a thin sheeted web. The lower curtains, and the upper retitelarian web are 
substantially the same in both. In other words, the typical character of 
an Orbweaver’s snare, namely, regular radiating lines regularly crossed by 
spiral concentrics, appears in the web of Basilica without any other change 
from a fixed generic Linyphian web. In the figure (157) the three netted 
domes were apparently made successively by one spider, and abandoned 
for some undiscovered reason. The ordinary web contains only one dome. 
It is probable that the curtain usually found beneath this is the compressed 
remains of a former dome, above which a new tent is reared. Something 
of the same habit may be seen in certain Orbweayers, who, however, push 
the rejected material to the outer margins instead of beneath the web. 
We may trace this interesting analogy from another point in the group 
of Orbweavers, and find yet further coincidence. The typical orb of the 
Fic, 157. The snare of Linyphia marginata. 
