THE BUTTERFLY AND f !T8 ALLIES 19 



from the stem. The moths of the genus Catocala, 1 which 

 fly by night, rest by day on the bark of trees, which they 

 so resemble as to be almost indistinguishable. Still more 

 striking is the resemblance which we find between some 

 adult butterflies and dry leaves as seen, for example, in Kal- 

 lima, a butterfly of the East Indies. 2 The resemblance of 

 the butterfly to the leaf extends even to details, for the 

 clear patches on the wing resemble holes, while little cir- 



FIG. 18. Catocala ilia, the underwing. Upper wings, bark color ; lower 

 wings, black with orange bands. Photo, by C. Bullard. 



cular markings resemble the patches made by particular 

 kinds of fungi. This resemblance of an organism to in- 

 animate objects in its environment is known as protective 

 resemblance. 



There are certain species of butterflies which appear to 

 be let alone by birds, owing to their disagreeable odor or 

 acrid taste. Examples of such are "the Heliconidse, char- 

 acteristic of tropical South America, and the Danaidse, to 

 which family our " Monarch " belongs. Closely resembling 

 1 Fig. 18. 2 Fig> 19. 



