XIV PROTECTIVE COLORATION 37 I 



inarch along in vast hordes, swarming over and tearing in pieces 

 any small animal which lies in tlieir path. They climb over 

 intervening obstacles, searching every cranny, and stripping them 

 bare of animal life. Insects which attempt to save themselves 

 l»y flight are preyed upon by the birds, which are always to be 

 seen hovering above the advancing army. The spider's only 

 resource is to hang from its thread in mid-air beneath the branch 

 over which the ants are swarming, for the spider line is imprac- 

 ticable to the ant. Belt ^ has observed a spider escape the general 

 destruction by this means. 



Protective Coloration. — Examples are numerous in which 

 the spider relies upon tlie inconspicuousness not of its nest, but 

 of itself, to escape its natural foes. Its general hues and 

 markings are either such as to render it not readily distinguish- 

 able among its ordinary surroundings, or the principle has been 

 carried still further, and a special ol^ject has been " mimicked " 

 with more or less fidelity. 



This country is not rich in the more striking mimetic forms, 

 but the observer cannot fail to notice a very general correspond- 

 ence in hue between the spiders of various habits of life and their 

 environment. Those which run on the ground are usually dull- 

 coloured ; tree-living species affect grey and green tints, and those 

 which hunt their food amongst sand and stones are frequently so 

 mottled with yellow, red, and grey, that they can scarcely be 

 recognised except when in motion. 



A few of our indigenous species may be mentioned as espe- 

 cially protected by their colour and conformation. Tihdlus oUongus 

 is a straw-coloured spider with an elongated body, which lives 

 among dry grass and rushes. When alarmed it clings closely to 

 a dry stem, remains motionless, and escapes observation by its 

 peculiarity of colour and shape. Misumena vatia, another of 

 the Thomisidae or Crab-spiders, approximates in colour to the 

 flowers in which it is accustomed to lurk on the watch for prey. 

 It is of a variable hue, generally yellow or pink, and some 

 observers believe that they have seen it gently waving its anterior 

 legs in a way which made them easily mistaken for the stamens 

 of the flower stirred by the breeze. Its purpose appears to be to 

 deceive, not its enemies, but its victims. It seems to be partial 

 to the blooms of the great mullein {Verhascum thapsus), and 



' The Naturalist in Nicaraijua, p. 19. 



