MAYER: COLOR AND COLOR -rATTERNS. 213 



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 niargin 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 184). 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 



