BURROWING HABITS OF SPIDERS. 33 
of portico for the spider when it is on guard. (Fig. 14.) The silk lining of 
the walls of the burrow (Fig. 16, sw) is continued along one side of the 
under surface (s) of the door by a thickened ribbon of silk (h), which 
‘serves the purpose of a hinge upon which the lid turns when it opens and 
shuts; its motion backward, however, is limited, for if one tries to bend it 
beyond the vertical the hinge is fractured. 
It will be seen from the section view of the upper part of the burrow 
(Figs. 15, 16) that the lid is much thickened toward the front, forming a 
crest, (cr), while the hinder part next the hinge has only a thin 
mr Lid coat of soil. This arrangement, Mr. Wagner points out, serves to 
Hinge bear down the free end of the lid, and closes it rapidly and tightly 
when the spider enters or goes forth; it has, in fact, the advan- 
tage of the strong and elastic hinge of the Trapdoor spider’s nest, which 
unites with the gravity of the door to bring it down into the burrow’s mouth. 
Some time before sunset, and probably during the day, Tarentula opifex 
may be seen on guard at the mouth of its den (Fig. 14) ; its head and fore 
COMPARATIVE VIEW OF TERRITELARIAN ARCHITECTURE. 
Fic. 20. Simple burrow (Mygale), unlined or lined only at top. Fic. 21. Purseweb spider’s tubular nest 
supported on trees; burrow. sparsely lined, covered with sand, wood, and mould. Fic. 22. Atypus piceus; 
low hung tubular nest without opening, covered with vegetable miscellany. 1G. 23. Silken rial tower, 
Leptopelma elongata. Fic, 24. Conglomerate tower, doorless. Fic. 25, Conglomerate tower, with wafer 
lid. Fie. 26. Burrow, with lid at the surface; silken lining. Fic. 27. Thick door, many layers, beveled 
edge, burrow completely lined with heavy silk. 
legs are then thrust over the margin of the door, which hangs ajar, and is 
supported upon the head and back. Here it will remain for a while as 
though on sentry duty until it ventures forth in search of prey. It is only 
when thus awaiting at its partly open door that it can be well seen; at 
the least movement of the observer or at sight of his approach the spider 
plunges into its burrow, the lid drops heavily, being borne down by the 
mass of soil accumulated at the crest (cr), and when closed it so closely 
resembles, the surrounding surface that it is nearly impossible to discover it. 
Here, now, is the one link which was wanting to entirely connect the 
architecture of the Lycosids with that of the Tunnelweavers, and complete 
that resemblance which I had pointed out. The series as thus completed 
may be arranged as represented at Figs. 20-32. Mr. Wagner has referred 
to the general likeness between the nest of his Opifex and that of the 
typical Trapdoor spiders, Nemesia or Cteniza, but has dwelt even more upon 
