THE HUNTING SPIDERS 221 



to deceive even trained naturalists and to some of them the word 

 "mimic" is with good reason applied. All the antlike spiders have 

 quite slender bodies and relatively long and thin legs. In certain 

 cases there are deep constrictions in the cephalothorax and abdo- 

 men, with these parts narrowed to expose the pedicel. In other 

 varieties only the abdomen is constricted, or a seeming division of 

 the body into several segments is accomplished by white bands 

 across the abdomen and cephalothorax without actual physical con- 

 striction. The spiders are small, and approximate in size and color 

 the ants they reputedly mimic. 



Whereas the physical resemblance to ants may be a natural con- 

 sequence of exploratory body growth within normal range of the 

 family, thus mere parallelism, there is reason to believe that some 

 degree of physical immunity, perhaps only slight at first, was the 

 result of the antlike form. To the best mimics would accrue the 

 greatest immunity from those normal enemies of spiders that hesi- 

 tate to attack ants. The imitation of ant movement has been instru- 

 mental in bringing even greater advantages to the spiders, and 

 probably has made unnecessary more profound changes in the body 

 itself. The mimics assume the particular stance, walk with the 

 same gait, elevate the abdomen, and move their legs in the manner 

 characteristic of the models. However, when they are disturbed, 

 the assumed posturing and gait are usually dropped, and the spider 

 departs the scene in spiderlike fashion. Whether the mimicry is 

 a real thing or just the figment of the observer's imagination re- 

 mains a moot point, but the advantages to the spider are unques- 

 tionable. Our best physical mimics belong to the genus Synemo- 

 syna. The commonest species is Synemosyna formica, a slender 

 black or brownish spider, about a quarter of an inch long, with deep 

 constrictions in the cephalothorax and abdomen. Amazingly antlike 

 in form, it walks and runs much as do ants, and uses its front legs as 

 ants use their antennae. Formica does not run in ant columns or live 

 in nests; it derives advantage only from its form. A Florida relative 

 is golden brown in color, and is often found running on folige with 

 ants of the genus Pseudomyrma; if this is its habitual environment, 

 presumably it would have even greater immunity than its darker 

 congener. 



Although we have several other genera and species of antlike 

 jumping spiders, mention will be made only of one more. Peck- 

 hamia picata is a small black spider with lightly constricted abdo- 

 men and quite thick front legs, which is undeniably antlike in form 

 and actions, but is not identified as the mimic of any particular 



