184 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
are to be seen in certain specimens of various species of the 
Heliconidae. For example, in Heliconius eucrate (Fig. 58, Plate 
4) I have observed that certain specimens show a row of distinct 
spots in place of the, usually entire, band which crosses the middle 
of the hind wing. In fact, the vast majority of bands can be 
analyzed into a series of similar elements, each element occupying an 
interspace. Thus, in Plate 2, Fig. 17, which represents a wing of 
Saturnia spini, the band seen crossing the wing parallel with its 
margin is made up of a series of fused crescents, each crescent 
occupying an interspace, 
If, on the other hand, this band were to break away from the 
nervures, tiie result would be a series of crescent-shaped spots each 
occupying the center of an interspace. It is very interesting to 
observe the manner in which bands degenerate and disappear. 
Numerous opportunities for doing this may be had among the Heli- 
conidae. In some species, as in Melinaea parallelis, hardly any two 
specimens are alike in the condition of the black band across the 
middle of the hind wings. The most common method of disappear- 
ance is a shrinking away of the band at one end. This is wellillus- 
trated in Figs. 84-87, Plate 7, which represent a sort of ** Mercator’s 
Projection " of the wings of Mechanitis isthmia (for explanation of the 
plan of projection see page 207.) Fig. 84 represents a male, showing 
a well-marked band of hardly separated spots extending across the 
middle of the hind wing. Fig. 87 shows a female in which the 
spots are thinner and more crescentic and the separations much 
more marked. Fig. 85 is also drawn from a female, in which it will 
be seen that the band has shrunk away leaving only a portion of it 
at the right, and in Fig. 86, which represents another female speci- 
men, only one faint spot is left. 
It is very common to find bands shrinking away at one end. 
Sometimes, however, they shrink away at both ends, and very often 
they break up into a row of spots, which may then contract into the 
centers of their interspaces and finally disappear. It is worthy of 
note that it is very rare to find a band breaking at the middle of its 
length and each half receding from the other. Such a case is, how- 
ever, shown by Melinaea parallelis (see Fig. 82, Plate 7), where one 
sometimes finds specimens in which the black band across the middle 
of the hind wings is complete and unbroken; whereas in other 
specimens, as in Fig. 82, it is partially broken in the middle, and in 
still others the break has become a wide gap by the drawing away of 
the halves of the band from each other. 
