KELLOGG: TAXONOiSIIC VALUE OF SCALES OF LEPIDOPTERA. 7 I 



Stiff scales and a regular arrangement of them, such specialized scales 

 much better serve to produce those striking colors due to inter- 

 ference, than do the generalized scale-hairs. And a uniform arrange- 

 ment, by bringing about regular overlapping, also aids in the production 

 of these colors. So that for the best performance of the color 

 function (the production of sharply-defined color-markings and of 

 brilliant tints) a specialization of the wing-covering is desirable, which, 

 both in form of the scales and their arrangement, is quite parallel or 

 identical with that specialization which best subserves the function 

 of strengthening the wing-membrane. 



As color-markings exist among Lepidoptera for protective resem- 

 blance or for attractive ornamentation,* in a word, for use, day- 

 flyers would of course, present a special development of color. In 

 the day-flyers the function of the scales as color and marking pro- 

 ducers is of great importance. It is probable that the great 

 specialization of the wing-covering of the butterflies is more 

 dependent on color function than on the strengthening function. 

 This very specialization of the scales, though, for color effect, mov- 

 ing along the same lines as the specializing for strength, brings it 

 about that both functions are the best subserved in these specialized 

 day-flying Lepidoptera. It is true, at any rate, that the specialization 

 of the wings of butterflies (shown by venation) for powerful flight 

 such as possessed by the Sphingids and some Zyg?enids is not com- 

 parable with the wing specialization of these Sphingids and 

 Zygeenids. The butterflies have a flight peculiar to themselves, 

 however, which is very effective in saving them from capture 

 while on the wing, and which, as a kind of flight especially adapted to 

 their needs, is accompanied by a distinct line of venation special- 

 ization. 



The specialization of the scales on the wings of Lepidoptera under 

 the special influence of their color function, will accompany those 

 advantageous occurrences of color and markings which are exhibited 

 among the moths and butterflies. For example, in the Arctiidje 

 there are many forms in which the forewings show a considerable 

 amount of color-marking or pattern while the hindwings, which are 

 quite covered by the forewings when the moth is at rest, are without 

 pattern. The scale-covering of the forewings in these cases, as in 

 Halesidota argentata and AracJuiis picta, is more specialized than 

 that of the hindwings. This, however, would be expected because of 

 the greater importance in flight of the forewings, accompanied by a 



*It Is probable that the patterns of Lepidoptera are not the result of sexual selection, 

 1. e.. are not for attractive ornamentation, considering the poor eyesight of these insects. 

 More likely the colors and patterns are the result of natural selection, producing the 

 familiar conditions of mimicry for protection. 



