222 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



(G) 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 Ileliconidae 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 Ileliconidae. 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 inaccux-racy 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 

 w^ing 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 220). Indeed, a good instance of this gi*eater 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 

 doAvnward, 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 



