184 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



are to be seen in certain specimens of various species of the 

 Heliconidae. For example, in Heliconiiis eucrate (Fig. 58, Plate 

 4) I have obsei'ved that certain specimens show a row of distinct 

 spots in place of the, usually entu-e, 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 liand were to break away from the 

 nervures, the 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 maybe 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 m,ethod of disaj^pear- 

 ance is a shrinJcing away of the hand at one end. This is well illus- 

 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 portioTi of it 

 at the right, and in Fig. 8(i, which represents another female speci- 

 men, on\y 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 parallehs (see Fig. ^'1, 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. 



