226 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
other examples which show that there is no lack of individual vari- 
ability among the Heliconidae. Yet the Danaoid species as a whole 
vary but little from the two great types 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 pleasure to me. I wish 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 numerous kindnesses, and who placed at my dis- 
posal the extensive entomologicai collections and library of the 
Museum of Comparative Zodlogy 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 library; to Prof. Ogden N. 
Rood for his valuable suggestions in regard to the spectroscopic 
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 
dises and the direct-vision spectroscope. 
PART C. 
GENERAL SUMMARY OF RESULTS BELIEVED TO 
BE NEW TO SCIENCE, 
(1) The great majority of the colors of Lepidoptera contain a 
surprisingly large percentage of black (p. 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 
