MIMICRY IN Sl'IDEKS. 357 



constructs a tube with a trapdoor opening, in every respect resembling 

 that of species which burrow in the ground, except that the tube is placed 

 upon the bark of various trees and ordinarily lodged within 

 Tree ^^g furrows of the same. Mr. Simon ' found specimens of these 



■I rap- upon trees of Venezuela, South America, and I have seen a num- 



uOOI*S 



ber of examples in the collection of the British Museum at Ken- 

 sington, London. Tliese were of various sizes, some of them witli doors 

 no larger than a pin head, yet perfectly constructed and exact miniatures 

 of that made by the adult. The utility of this mimicry is apparent. The 

 insects which alight and walk on trees, must often go over and around 

 this trap, which in appearance and texture so closely resembles its site. 

 Thus opportunity and facility arc afforded the spider, waiting at its partly 

 open door, to seize its prey. 



11. 



Among s})iders, the form of other animals is sometimes mimicked. The 

 most striking example is that of the little group of araneads whicli, by 

 stricture of the abdomen and shape of the head, are made to 

 Form resemble tlie form of certain ants. Simonella americana Peck- 

 imicry j^^^^^ ^^ ^^^ example of this form mimicry. (Fig. 315.) One 

 mals specimen of this spider is recorded as having been found run- 



ning among leaf cutting ants.^ Certainly there is a sufficient 

 resemblance between the two creatures to permit one to think that a spi- 

 der so formed might run upon the ground among a marching or working 

 column of these emmets without any great fear of detection, provided 

 the ants had no better means of discovering the presence of friend or foe 

 than their eyesight. As a matter of fact, however, their 

 principal means of observation in this respect ajipears to be ^.^^jj^ 



the sensitive antennse. Having closely studied the habits of — 



the leaf cutting ants, Atta fervens/' in Texas, I cannot "^'i:,''*- .*" °""'".« 



o ' - ' ' side view of Si- 



readily think that any spider, or any other creat- moneiia america- 

 "S^ere^ ure at all obnoxious to tlicse ants, whatever might ^am'T" ''*"'" 



be its form, would have been permitted to remain 



in the way of the immense swarms of insects that issue in the evening 

 from their formicary, and go forth upon their predatory expeditions into 

 the surrounding foliage. 



Another of these ant formed spiders, which belongs to our indigenous 

 fauna, is Synemosyna formica Hentz. (Fig. 316.) The figure is drawn 

 from a specimen sent me by Professor Peckham, but the species is quite 

 widely distributed over the United States, having been originally de- 

 scribed by Hentz. Yet another spider which certainly bears a striking 



• Ann. Soc. Entom. de France, 1889, page 220, plate i., Fig. 3. 



^ Spiders of the Subfamily Lyssonian!v>, Trans. Wisconsin Acad. Sci., 1888, page 252. 



" Proceed. Acad. Nat. Sci., Phila., 1879, page 33. 



•• Proced. Nat. Hist. Soc. Wisconsin, 1885, plate i., Fig. 1. 



