OF WILD ANIMALS 47 



near the edge, precisely placed where the curved fangs may be 

 inserted and the door held firmly closed. Also, the trap-door 

 of a number of species is so designed as to be absolutely rain- 

 proof, being bevelled and as accurately fitting a corresponding 

 bevel of the tube as the setting of a compression valve of 

 a gasolene engine. 



"The study of a number of specimens of our southern 

 California species, which builds the cork-type door, including 

 observations of them at night, when they are particularly 

 active, indicates that the construction of the tube involves 

 other material than the silken lining employed by many 

 burrowing spiders. In the excavation of the tube and retention 

 of the walls, the spider appears to employ a glairy substance, 

 which thoroughly saturates the soil and renders the interior 

 of the tube of almost cement-like hardness. It is then plastered 

 with a thick jet of silk from the spinning glands. This in- 

 terior finishing process appears to be quite rapid, a burrow 

 being readily lined within a couple of hours. 



"The construction of the trap-door is a far more complicated 

 process, this convex, beautifully bevelled entrance with its 

 hinge requiring real scientific skill. Judging from observations 

 on a number of specimens, the work is done from the outside, 

 the spider first spinning a net-like covering over the mouth of 

 the tube. This is thickened by weaving the body over the 

 net, each motion leaving a smoky trail of silk. Earth is then 

 shoveled into the covering, the spider carefully pushing the 

 particles toward the centre, which soon sags, and assumes the 

 proper curvature, and automatically moulds against the 

 bevelled walls of the tube. 



"The shoveling process must be nicely regulated to produce 

 the proper bevel and thickness of the door. Then the cement- 

 ing process is applied to the top, rendering the door a solid 

 unit. From the actions of these spiders, which often calmly 

 rest an hour without a move, it appears that the edges of 

 the door are now subjected, by the stout and sharp fangs, to 



