356 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



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only be detected beneath the bottom of the tube, layers of silk having 

 been spun over successive layers of refuse. The liorny crops of ants form 

 by far the largest proportion of these remains, and Moggridge was struck 

 by the number of instances in which, while digging out ants' nests at 

 Mentone, he found Trapdoor burrows, especially those of Nemesia mander- 

 stjernae and Nemesia moggridgii in their midst, the tubes often traversing 

 the very heart of the ants' colony, and coming into close contact with 

 their galleries and chambers. 



In these instances the trapdoors had almost always escajjed his notice, 

 and, indeed, they so closely resembled the surface of the ground that even 

 when he knew, from having accidentally cut across the tube below the 

 ground, that one of these doors must lie near a given spot, yet he could 

 only discover it by following the passage below upwards. This perfect 

 concealment the discoverer tliought of essential importance to the spider's 

 success in life, for if they once alarmed the whole colony of ants and let 



them know the exact whereabouts of their 

 lurking place, they would soon learn to 

 avoid it.^ 



The fact of mimetic resemblance in the 

 tubular snare of the Purseweb spider has 

 already been alluded to. I have seen hun- 

 dreds of these in various parts of Florida, 

 and have before me several score speci- 

 mens. These are covered on the outside 

 with particles of sand, and even more free- 

 ly with the brown wood mold which has 

 accumulated in large quantities around the 

 trunks of trees in Floridian forests where 

 the spider abounds. The resemblance of 

 the tube to the bark of the tree against 

 which it is planted is close, much closer, 

 in most cases, than is represented in the 

 drawing Plate II., Fig. 7. As the spider 

 is dependent for her suppl}'^ of food upon 

 the number of insects that crawl upon her tube, we may supjsose that 

 she derives considerable advantage from this resemblance, inas- 



S 



Fig. 314. The tree Trapdoor spider's nest, 

 Pseudidiops opife.x. (After Simon.) 



„ . , much as it allows her to creep upward to where her victim rests, 



or encourages the victim to crawl towards the jioint where she 

 lies in wait to ding her web around it. 



An exami)le of nest architecture among Trapdoor spiders wliich may 

 be classed in the same category as the above, is a species whicli Mr. Eu- 

 gene Simon describes as Pseudidiops opifex. (See Fig. 314.) This aranead 



Trapdoor Spiders, Supplement, page 237. 



