218 BULLETIN: MUSEUM* OF COIVIPARATIVE ZOOLOGY. 



both foi-e and hind wings are very similar. In order to exhil)it this 

 fact graphically, the color-variations have been laid off upon the 

 diagram, Fig. 97, Plate 9. The base hne is marked at equal inter- 

 vals with the words " rufous," " translucent rufous," " translucent, 

 slightly rufous," " transparent," etc., and the ordinates show the 

 number of species which exhibit the various colors, rufous, trans- 

 lucent rufous, etc. For example, at the point " translucent rufous " 

 we find that the ordinate is 23 ; this indicates that in 23 species 

 the area is translucent rufous in color. The points thus found 

 upon the ordinates are successively joined by straight lines form- 

 ing a zig-zag figure. The full Hue represents the fore wing, and 

 the dotted line the hind wing, and it becomes clearly evident from 

 the closeness of these two zig-zag lines that the color of the inner 

 rufous area of the fore wing (area I, Plate 4) is almost always 

 sure to be identical with that of the inner rufous area of the hind 

 wing (area X, Plate 4). We see, therefore, that whatever color- 

 varittion affects the inner rufous area of the fore wing, this area 

 in the hind wing is almost always affected in the same manner. 



Fig. 99, Plate 9, is derived from Tables 15 and 24, which show 

 the color-variations in the fore and hind wings of the genera Hehco- 

 nius and Eueides. It is seen that here also the colors of these two 

 areas in both the fore and hind wings are almost always identical. 

 We here meet with one of those interesitng physiological laws 

 which are independent of Natural Selection, and the meaning of 

 which remains a mystery, for surely we can see no reason on the 

 ground of adaptation why similar areas upon both fore and hind 

 wing should bear similar colors. 



(2) The " Inner Black'' Spot. Table 2 shows the presence or 

 absence of the "inner black" spot in the Danaoid Heliconidae. 

 This spot is marked II in the figures upon Plate 4. When pres- 

 ent, it is alwavs black in color and is usually found occupying the 

 middle region of the cell of the fore wing. The table shows that 

 it is about an even chance whether it be present or not, for it is 

 absent in 210 species and present in 190. In the genus Ithomia, 

 however, it is present in only one third of the species. What is 

 most worthy of note concernmg it, is the fact that it almost always 

 appears, when present, as a single spot. Indeed, it appears as a 

 double spot in only 7 species, and 5 of these belong to the genus 

 Melinaea. A good example of its appearance as a double spot is 

 found in Melinaea paraiya (Fig. 48, Plate 4). It will be rem em- 



