MAYER: COLOR AKD COLOR-PATTERNS. 197 



As the scales have been developed not because they aided the 

 insects in flight or strengthened tlie wings, their retention must 

 liave been due to some other cause, probably to their display- 

 ing colors which were advantageous to their possessors in various 

 ways. As Dimmock ('8H) says, " it is only in insects where certain 

 kinds of brilliant coloration have been developed that one finds 

 scales." Indeed, I believe that the vast majority of the scales 

 found in Le])idoptera are merely color-bearing organs. They prob- 

 ably flrst made their appearance upon small areas of the wings, 

 perhaps adjacent to the body, and were merely colored hairs, sim- 

 ilar to those of the surface of the body, which had grown out upon 

 the wings. In this position they displayed some color which was 

 of advantage to the insect ; perhaps serving to render it less con- 

 spicuous than formerly. Under tliese circumstances they Avould 

 naturally be presei-ved through the operation of selection until 

 finally they became modified into true scales ; just as the hairs in 

 the Coleoptera have undergone a similar modification. If this 

 be true, it is easy to see how they might spread out over 

 the surfaces of the wings until the whole wing became covered 

 with scales. 



(2) /Summary of Conclusions. The scales do not aid the insects 

 in flight, for the wings have precisely the same efliciency as organs 

 of flight when the scales are removed. The phylogenetic appearance 

 and development of the scales upon the scaleless ancestors of the 

 Lepidoptera did not in the least alter the efliciency of their wings as 

 organs of flight. This efliciency of their wing surfaces was probably, 

 therefore, already an optimum before the scales appeared. The 

 scales do not appreciably strengthen the wing-membranes, that 

 function being performed by the nervures. The majority of the 

 scales are merely color-bearing organs, Av^hich have been developed 

 under the influence of Natural Selection. 



PART B. 



COLOR- VARIATIONS IX THE HELICONIDAE. 



I. General Causes which dp:tp:rmine Coloration in the 



Heliconidae. 



In 18G1, after eleven years of study within the forests of South 

 America, Bates read his, now classic, jjaper upon the life and habits 



