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ORGANIC EVOLUTION 



and some particular object, the animal escaping detection 

 because of this resemblance. Often the animal has peculiar 

 habits which make the resemblance more perfect. Among 

 insects these special resemblances are not uncommon. One 

 of the best examples is the caterpillar of the brimstone moth, 

 which resembles a twig, and which remains motionless in 

 just the position to make this resemblance most perfect. In 



color, shape, and habit- 

 ual position the resem- 

 blance is very exact. 

 The caterpillars of many 

 other species of moths 

 show a similar resem- 

 blance to twigs (Fig. 30 

 and Plate 60). Some 

 caterpillars resemble 

 the ragged edges of the 

 leaves of their food- 

 plant, both color and 

 shape making a striking 



FlG. 30. Twig-like caterpillar of the moth Selenia resemblance (Plate S^). 

 tetralunaria, on a spray of birch. [After WEISMANN.] 



K. The head. F. The feet. M. A mark resem- Other Caterpillars are 



bling a bud scar. .. , -, 



green with brown spots, 



conforming closely in color and color pattern to the fungus- 

 spotted leaves upon which they are found (Plate 56). Some 

 adult insects resemble sticks ; for example, the common 

 "walking-stick" (Plate 61, A). In Nicaragua there is 

 found a walking-stick in which the deception is carried still 

 farther by certain excrescences on the body and legs which 

 cause it to resemble a bit of moss (Plate 61, ^). Belt, its 

 discoverer, says it is found on moss. Many insects resemble 



