296 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
(6) The relative Permanency of the Black Areas upon the Fore 
and Hind Wings. A study of the relative permanency of the 
various characteristic black markings upon the wings is of interest, 
for, if the generally accepted idea concerning the prevalence of 
mimicry within the group of the Danaoid Heliconidae be true, we 
should expect the most conspicuous markings to be the most perma¬ 
nent, for they are evidently of the most importance for mimicry. 
This is, however, not the case for the black markings. A good 
example of this fact is afforded by a comparison of the relative 
permanency of the black streak which extends along the extreme 
costal edge of the fore wing with the inner black spot (II in figures 
on Plate 4 ). The inner black spot is certainly a more conspicuous 
marking than this narrow black streak along the costal edge; yet it 
is much more variable, for Table 2 shows that it is present in 210 
and absent in 190 of the 400 Danaoid Heliconidae. In other words, 
it is about as likely to be present as absent. The black streak upon 
the costal edge, on the other hand, is much more permanent, for it is 
absent in only 52 species out of the 400. 
Another good example of the inaccurracy of the supposition that 
large and conspicuously colored areas are always less variable than 
small ones, is derived from a comparison of the relative variability 
of the large outer black of the fore wing with the small outer 
black of the hind wing. Although the outer black area of the fore 
wing is usually much larger and more conspicuous than the outer 
black margin of the hind wing, it is more variable in color, for it is 
rufous in 22 species, while the outer black of the hind wing is 
rufous in only 11, out of the 400. 
In general, however, large colored areas are more permanent than 
small ones, as was found in the case of the inner and middle yellow 
areas (see page 294). Indeed, a good instance of this greater vari¬ 
ability of small color areas is afforded by the longitudinal black 
stripe marked VIII in the figures of Plate 4 , for this is more 
variable than the larger outer black area of the fore wing. 
(7) The “ Middle Black Stripe ” of the Hind Wing. In the 
genus Ithomia the middle black stripe (XI, Plate 4 ) has migrated 
downward, so that in many species it has become fused with the 
outer black margin, as in Ithomia sao (Fig. 52, Plate 4 ). In other 
cases there is still to be seen a narrow line of rufous color between 
the middle black band and the outer black margin of the hind 
wing. Such is the case in Ithomia nise (Fig. 54, Plate 4 ). In 
