226 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 



Other examples which show that tliere is no lack of individual vari- 

 ability among the Heliconidae. Yet the Danaoid species as a whole 

 vary but httle from the two great tyjies of coloration represented 

 by Ithomia and Melinaea, and in this respect they are very differ- 

 ent from the Papilios, where we find a great many color-types and 

 great diversity in shape of wings. Surely there must be some cause 

 for the remarkable fact that the Danaoid Heliconidae with their 

 453 species should display but two types of color-pattern. I can 

 think of but one explanation, which is afforded by Fritz Miiller's 

 theory of mimicry. 



In conclusion it gives me pleasure to thank those friends whose 

 generous aid and kindness have done so much to render the prose- 

 cution of this research a pleasiu*e to me. I ^Wsh to express my 

 gratitude to Dr. Charles B. Davenport, who is the real instigator 

 and promoter of this research ; to Mr. Samuel Henshaw, to whom 

 I am indebted for numeroiis kindnesses, and who placed at my dis- 

 posal the extensive entomological collections and library of the 

 Museum of Comparative Zoology at Harvard ; to Prof. Edward L. 

 Mark for his kindness in revising the manuscript of this paper, and 

 for the numerous valuable suggestions which he has made ; to Dr. 

 Samuel H. Scudder, to whom I am grateful for much kind advice 

 and for the use of rare works in his Ubrary ; to Prof. Ogden X. 

 Rood for his valuable suggestions in regard to the sjjectroscopic 

 apparatus ; to Dr. Alpheus Hyatt for his valued and kind advice, 

 and to my father, Prof. Alfred M. Mayer, for the use of Maxwell's 

 discs and the direct-vision spectroscope. 



PART C. 



GEXERAL SUMMARY OF RESULTS BELIEVED TO 

 BE XEW TO SCIENCE. 



(1) The great majority of the colors of Lepidoptera contain a 

 surprisingly large percentage of black fp. 172). 



(2) The colors displayed by the scales are not simple, but com- 

 pounded of several different colors (p. 173). 



(3) The pigments of the scales of Lepidoptera are derived by 

 various chemical processes from the blood, or haemolymph, of the 



