GENERAL COCOONING HABITS OF SPIDERS. 



139 



That accomplished French arachnologist, M. Eugene Simon, has recently 



added largely to our knowledge of this interesting tribe. A visit to South 



America enabled him to make personal studies of trapdoor nests, 



imon on ^^ these have happily found expression in admirably drawn 



Spiders plates, some of whose figures I have ventured to redraw for these 



pages. Rhytidicolus structor is a common species in Venezuela, 



particularly upon the slopes of compact and sandy ground. Its burrow is 



the most complex that Simon observed. It is composed of three successive 



spacious chambers, communicating one with another by straight openings, 



which close by a hinged door. 



The first chamber is largely dilated in the form of a pear, but quite 

 contracted at the two extremities. (See Fig. 170.) The second chamber is 

 more or less cylindrical, and termi- 

 nates in a cul de sac. The third 

 chamber communicates with the sec- 

 ond, not by its extremity, but upon 

 the side, which is dilated and oval, 

 like the first, and rounded at the bot- 

 tom. The walls of the entire burrow 

 are perfectly built, very smooth, and 

 draped with a white tissue, light, 

 transparent, and adhering. The three 

 doors are almost alike. They are 

 thick, cut like a stopple upon the edge, 

 and penetrate within the opening, 

 which is itself slightly widened and a 

 little prolonged beyond the surface. 

 They are semicircular, and cut in a 

 straight line on the side of the hinge. 

 Their superior faces are rough, like 

 the adjoining soil, even with the in- 

 side doors ; sometimes at an external 

 opening the doors are a little swollen, 

 and very unequal, but always slightly concave on the internal doors. The 

 internal faces of the doors are convex, and have a silk drapery like that 

 of the walls. On the edge of the bevel are small holes for the attachment 

 of the claws when the trap is to be .held down, and these are more distinct 

 on the entrance door. This swings naturally from within to the out- 

 side. The second door opens, on the contrary, from the outside inwardly 

 in such manner that in the first chamber the two doors show the inter- 

 nal faces equally smooth. The arrangement of these doors is shown in 

 the figure. 



The female deposits her eggs in the first chamber; they are not agglu- 

 tinated, and are enveloped in a cocoon of white, opaque tissue, much longer 



FIG. 170. Section in the earth, showing trapdoor 

 nest of the female Khytidicolus structor. (After 

 Simon.) FIG. 171. Outline of first chamber of 

 Ehytidicolus structor, to show location of cocoon. 



