MAYER: COLOR AND COLOR-PATTERNS. 
287 
Plate 7 is intended to illustrate the peculiarities of color-pattern 
found among the Danaoid Heliconidae. Thyridia psidii (Fig. 79) 
is an example of the transparent type of color-pattern found among 
the Danaoid Heliconidae, and especially prevalent among the 
Ithomias. It will be seen by comparing Fig. 79 with the other 
figures upon Plates 7 and 8 , that the chief difference lies in the fact, 
that in this type both the rufous and yellow areas have become 
transparent. The black area of the fore wing has also suffered a 
reduction, especially along the outer margin of the wing. Inci¬ 
dentally it should be mentioned, that in this particular species the 
middle black band of the hind wing has become tilted up at a sharp 
angle, instead of crossing the wing horizontally. A life-size figure 
of the wings of Thyridia psidii is given on Plate 4 , Fig. 47. 
In Napeogenes cyrianassa (Fig. 80) and Ceratinia vallonia (Fig. 
81) portions of the usually yellow and rufous areas have become 
transparent. 
The spots upon the fore wing of the Melinaeas are usually yellow, 
but in Melinaea parallelis (Fig. 82) they are white. It would seem 
that this form may have descended from some albinic sport. 
Ceratinia leucania (Fig. 83) resembles Melinaea parallelis so closely 
in general plan of coloration, that it is very difficult to distinguish 
between them, even when the two insects are seen side by side. 
Ceratinia leucania, however, is somewhat smaller than Melinaea 
parallelis. Both occupy the same region in Central America, and 
the specimens from which the diagrams were drawn came from 
Panama. 
Figs. 84-87 are drawn from various specimens of Mechanitis 
isthmia, all from Panama. They are intended to give some idea of 
the range of individual variation which is met with in this extremely 
variable form. The contraction of the middle black band of the 
hind wing in this form has already been noticed in the general 
discussion of the laws of color-pattern (see page 258). In Fig 87 it 
will be seen that the inner yellow stripe which usually crosses the cell 
of the fore wing has become very narrow and changed to a rufous 
color. However, upon the under surface of the wing it still remains 
as a yellow stripe. Indeed, in most color-changes the upper side of 
the wing seems to take the initiative, the under surface being more 
conservative. This is not true, however, in the Ithomias, where 
the black areas of the under side of the wings often are found to be 
rufous in color, while they still remain of the normal black upon the 
