MIMICRY IN SPIDERS. 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 the furrows of the same. Mr. Simon * found specimens of these 



rap- U pon trees of Venezuela, South America, and I have seen a num- 

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

 sington, London. These were of various sizes, some of them with 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 are afforded the spider, waiting at its partly 

 open door, to seize its prey. 



II. 



Among spiders, the form of other animals is sometimes mimicked. The 

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

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

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

 imic.ry ham is an 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. 2 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 appears to be ^/Jjl 



the sensitive antennae. Having closely studied the habits of ^ 

 the leaf cutting ants, Atta fervens, 3 in Texas, I cannot FIG 315 An outline 



e ' side view of 81- 



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



Spkler? ure at a11 obnoxious to these ants > whatever might Sa 



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 Heiitz. (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 



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



2 Spiders of the Subfamily Lyssomanse, Trans. Wisconsin Acad. Sci., 1888, page 252. 



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



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



