288 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
upper surface. The colors of the under surface are, however, 
usually identical with those of the upper, though they are always 
duller in 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 jiaraiya (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. General Discussion of the Color-Patterns and of 
Mimicry among the Danaoid Heliconidae. 
(1) The Origin of the Two Types of Coloration. The character 
of the variation in the Danaoid Heliconidae is very different from 
that of the genera Heliconius and Eueides, for while there is great 
