214 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



upper surface. The colors of the under surface are, however, 

 usually identical with those of the upper, thouo-h they are always 

 duller ill hue. This may be due to the fact, that the colors of the 

 upper surface are more frequently seen than those of the lower, for 

 these insects often float lazily along with their wings horizontally 

 extended. The operation of Natural Selection would then be more 

 severe with the upper surfaces than with the lower. 



Plate 8 gives an analysis of the color patterns of some of the 

 Heliconinae and those Melinaeas, etc., which they resemble. H, 

 eucoma (Fig. 88) is a good example of the Sylvanus type, and with 

 its rufous, yellow, and black wings it is certainly a wonderfully close 

 copy of the color-pattern found so commonly among the species of 

 the genus Melinaea of the Danaoid Heliconidae. 



Heliconius dryalus and Melinaea paraiya (Figs. 89, 90) resemble 

 each other so closely in size, shape, and coloration, that it must be 

 impossible to distinguish between them when the butterflies are in 

 flight ; yet an analysis of their color-patterns shows that there are 

 considerable differences between them. The shape of the yellow 

 bands upon the fore wings is quite different ; the inner black spot 

 within the cell is double in Melinaea paraiya, and there is also a row 

 of white spots along the margin of the fore wing. 



A much closer resemblance is found between H. eucrate and 

 Melinaea thera (Figs, 91 and 92), where the Heliconius is almost a 

 true copy of the Melinaea. 



The color-patterns of Eueides dianasa (Fig. 93) and Mechanitis 

 polymnia (Fig. 94) are also very nearly the same. Both are 

 common species in Brazil. 



Heliconius sylvana is said by Bates and by Wallace to mimic 

 Melinaea egina. It will be seen by reference to Figs. 95 and 96 

 that their color-patterns are quite different in detail, yet the insects 

 look very much alike when placed side by side, and may easily be 

 mistaken for each other when upon the wing. Melinaea egina is 

 much more common than Heliconius sylvana. 



IV. Gener.vl Discussion of the Color-Patterxs an^d of 

 Mimicry among the Danaoid Heliconidae. 



(1) The Origin of the Two Types of Coloration. The character 

 of the variation in the Danaoid lEeliconidae is very different from 

 that of the genera Heliconius and Eueides, for while there is great 



