Ei ARACHNIDA—ARANEAE CHAP. 
of the body, but the operation is effected by a special apparatus. 
These spiders are eribellate, and in front of the six ordinary 
spinnerets there are a pair of perforated plates connected with a 
large number of additional minute spinning glands (see Fig. 182, 
p- 326). In conjunction with this, the female possesses on the last 
joint but one of each hind leg a curious comb-like arrangement 
of spines, the “calamistrum.” The animal constructs a sort of 
skeleton web by means of its ordinary spinnerets, and when this 
is completed it combs out silk from the cribellum by means of 
the calamistrum, using each hind leg alternately, and distributes 
it with a curling motion upon the scaffolding prepared for it, 
a nearly opaque web being the result. The silk from the 
eribellum is of an adhesive nature, and renders escape from 
the web very difficult. 
Spiders’ Nests and Retreats.—A1] Spiders construct some 
description of nest, and often display great ingenuity in build- 
ing them. Perhaps none are more curious than those of the 
burrowing Aviculariidae, a family which includes the interesting 
“Trap-door Spiders.” They are nocturnal in their habits, about 
which, consequently, little is known, but their nests have been 
carefully studied, especially by Mogeridge, who found them in 
considerable abundance in various districts of the Riviera. 
The jaws of these spiders are especially adapted for digging, 
and with them a hole is excavated in the ground to the depth 
of several inches, and wide enough to allow the animal to turn. 
This is carefully lined with silk which the spider throws against 
the sides from its long and upturned posterior spinnerets. But 
the chef @wuvre of the whole structure is a lid or door which 
protects the entrance to the tube. There are two types of door 
which find favour with different species—the wafer and the 
cork type, as Mogeridge has named them. The former consists 
of a thin circular or oval sheet of silk which flaps down loosely 
over the tube-entrance, with which it is connected by a hinge- 
like attachment. A trap-door of the cork type is a more com- 
plicated structure, being of considerable thickness and having a 
bevelled edge, so that it fits into the tube like a plug. Like the 
wafer door, it possesses a silken hinge. 
To form the wafer door, the spider covers the entrance to the 
tube with a closely-woven layer of silk, which it afterwards bites 
away at the edge, except at the point where the hinge is to be. 
