BURROWING HABITS OF SPIDERS. 



33 



of portico for the spider when it is on guard. (Fig. 14.) Tlie silk lining of 

 tlie 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 tlie 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 

 The Lid ^^^^ q£ g^jj rpj^^g arrangement, Mr. Wagner points out, serves to 

 Hinee ^^^^ 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 



22 23 24 25 26 27 



Comparative View of Territelarian Architecture. 



Fig. 20. Simple burrow (Mygale), unlined or lined only at top. Fig. 21. Purseweb spider's tubular nest 

 supported on trees; burrow sparsely lined, covered with sand, wood, and mould. Fig. 22. Atypus piceus; 

 low hung tubular nest without opening, covered with vegetable miscelbiny. Via. 23. Silken serial tower, 

 Leptopelma elongata. Fn^ 24. Conglomerate tower, doorless. Fig. 25. Conglomerate tower, with wafer 

 lid. Fig. 26. Burrow, with lid at the surface; silken lining. Fig. 27. Thick door, many layers, beveled 

 edge, burrow completely lined with heavj' 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 apin-oach 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 tlie 

 typical Trapdoor spiders, Nemesia or Cteniza, but has dwelt even more upon 



