118 



BRANCH ARTHROPODA 



greens, . . . are due to the structural or physical make-up of the 

 scale covering." 1 



Variable Protective Resemblance. Often the different indi- 

 viduals of the same species are of slightly different colors, the 

 colors varying to harmonize with the particular environment 

 of the individual during its development, being fixed in the 

 adult, 



Special protective resemblance (Fig. 90) is illustrated by 

 Kallima, which resembles a dead leaf, and Phyllium, resembling 

 a green leaf (Fig. 91), and, more commonly, by the measuring- 

 worm, as it holds the body out stiff, imitating a short or broken 

 twig. Thus in many cases " the insect's appearance simulates 

 in more or less nearly exact ways some par- 

 ticular part of the habitual environment." 



Warning colors are possessed by many 

 insects having a special organ of defense 

 as the sting of that wonderful little 

 stimulator, the hornet or a disagreeable 

 taste or odor, as that of the milkweed or 

 " monarch " butterfly (Anosia plexippus) 

 (Fig. 92, a). Other examples of insects 

 having conspicuous or warning colors are 

 the black and yellow wasps and bees, the 

 lady-bird beetle, and the swallow-tail but- 

 terflies. Many others might be mentioned. 

 Since the bodies of insects are soft, one 

 can easily see why these conspicuous colors 

 are of natural advantage. A single stroke 

 of the beak of a bird might prove fatal 

 to any of them. The bird must learn by 

 experience that the insect is armed or distasteful, but if the 

 insect is conspicuously colored, it will be noticeable and easily 

 remembered, so that the bird will not attack another of this 

 brightly colored kind. Hence the species will be perpetuated 

 and the characteristic colors handed down to the next genera- 

 tion, or, in other words, " preserved and accumulated by natural 

 selection." 



Alluring or directing colors or forms may be found among in- 



1 Kellogg. 



Fig. 9l.Phyl'- 

 lium siccifo'lium 

 feeds on leaves, and 

 mimics fresh leaves. 

 (Holder.) 



