THE HUNTING SPIDERS 227 



The ability of Misumena calycina (or vatia) (Plates 3 and 27) 

 to change its color from white to yellow and vice versa was first 

 noted about seventy years ago. This fact engaged the attention of 

 many naturalists, and led, in some instances, to erroneous applica- 

 tion of the same principle to other spiders on little evidence, to 

 fantastic claims of change through many hues that have no basis 

 in fact. It can easily be demonstrated, however, that Misumena 

 calycina and many of her cousins can change, in the course of a 

 week or more, from white to yellow on a yellow flower or an arti- 

 ficial yellow substratum. The action is reversible, usually requiring 

 only five or six days. There is considerable reason to believe that 

 the immature stages of this spider are always white, and that the 

 changes in color are possible only for mature females, as was 

 claimed by Eugen Gabritschevshy, the French biologist. However, 

 both juvenile and adult examples of the closely allied Misumenoides 

 aleatorius (Plate 9 and Plate XXIX) of the United States may be 

 shining yellow, and are reputedly capable of changing back to 

 white. 



Because of peculiar body form, certain crab spiders have been 

 singled out as receiving some sort of protection from their natural 

 enemies through resemblance to inanimate objects. Phrynarachne 

 rugosa is said to resemble in form and color the fruit of a common 

 tree in its forest home. Another spider of the same genus, Phryn- 

 arachne decipiens (described under the appropriate name of Orni- 

 thoscatoides), is reputed to resemble the excreta of a bird, and the 

 illusion is complete when the spider has fashioned its characteristic 

 web. Other thomisids have been compared to dried seeds, leaf 

 buds, and various flower parts. 



THE RUNNING SPIDERS 



The running spiders are two-clawed vagrants that wander about 

 over the soil and on vegetation, aided in their movements by ad- 

 hesive tarsal claw tufts. In almost all instances the front legs are 

 directed forward and locomotion is normal or prograde, as con- 

 trasted with the laterigrade maneuvering of the crab spiders. Their 

 bodies, usually elongated and often cylindrical, are furnished with 

 quite stout legs, which propel them at great speed. Some rarely 

 leave ground hiding places under stones and debris, while others 

 climb actively over vegetation arid make their retreats in plants. 

 These running hunters, probably typical of the prototypes from 



