596 Color and Pattern and their Uses 



The blacks, browns, yellows, and dull reds of butterflies and moths, 

 then, are produced chiefly by pigment; while all the brilliant metallic colors, 

 the iridescent blues and greens, and hosts of allied shades, are due to the 

 structural or physical make-up of the scale-covering. The patterns, varied 

 and intricate, with lines and spots and bars, sharply deliminated or softly 

 merging into the ground color or into one another, depend on the fact that 

 the color-units, the scales, are so small that by the juxtaposition of scales 

 containing different pigments, or varying slightly in structure, different 

 colors may be produced abruptly or gradually, depending upon the degree of 

 differences in pigment and structure of adjacent scales. By the extremely 

 regular arrangement, in the higher moths and butterflies, of the short, rigid, 

 little scales, definite lines and sharp limits to spots and bars are possible. 

 In the lower, fluffy moths where the scales are hair-like and irregularly ar- 

 ranged such sharp delimitations of pattern parts are not possible. Thus 

 the specialization of the scales, both as to structure and arrangement, in 

 the brilliantly colored and complexly patterned day-flying Lepidoptera is 

 seen to be exactly connected with the specialization of color and pattern. 



The studies that have so far been made upon the character and origin 

 of types of pattern have brought some aspect of orderliness into what seems 

 at first glance a chaos of complexity, but our knowledge of this matter is 

 yet too little organized to make it available in such a brief general account 

 of insect color and pattern as this one necessarily is. In the actual develop- 



FIG. 784. Diagrammatic series showing development of color-pattern in pupal wings 

 of the monarch butterfly, Anosia plexippus. (After Mayer; one-half natural size.) 



ment or course of appearance of the color-pattern in the wings of any individual 

 moth or butterfly certain conditions regularly obtain, as shown by Van B em- 

 mem, Urech, Haase, Mayer, and others. Mayer's account and figures of 

 the development of color in the fore wings of the monarch butterfly, Anosia, 

 plexippus, show a typical case. The pupal stage of Anosia lasts from one 

 to two weeks. "For the first few days," says Mayer, "the wings are perfectly 

 transparent, but about five days before the butterfly issues they become pure 

 white. An examination of the scales at this period shows that they are 



