MAYER: COLOR AND COLOR-PATTERNS. 219 



bered that there are 450 species in the Danaoid group ; 25 of 

 these belong to the genus Melinaea ; yet among these 25 we find 

 5 exhibiting this marking as a double spot. Assuming that the 

 doubling of this spot has arisen in each species as a sport, and that 

 such a sport is as likely to appear in one species as in any other of 

 the Danaoid group, then the chances against five such sports 

 appearing among the 25 Melinaeas is ^''^^^!l^''^.t^l'^!^\ or about 

 2,830,000 to 1. Indeed, it is probable that all five of the species 

 of Melinaea which exhibit the doubhng of this spot are descend- 

 ants of a sinffle ancestor in which it appeared for the first time 

 double, for the mathematical chance that one such ancestor should 

 appear among the Melinaeas, rather than in any other genus, is 

 evidently 1 in ~, or one chance in eighteen. The chance against 

 two such unrelated ancestors is, however, !5^><:^ or about 336 to 



25x24 ' 



1, and the chance against three is "gggg-^ or 6,560 to 1, etc. 



By reference to Table 16 we find that in the genera Heliconius 

 and Eueides the inner black area is black or iridescent blue in all 

 of the species of Heliconius, but absent in 5 of the 18 species of 

 Eueides known to me. These 5 include Eueides aliphera and its 

 alhes. Now there are 150 known species of the Acraeoid Helico- 

 nidae, and 24 of these belong to the genus Eueides ; so it is evident 

 that the mathematical chance against the supposition that five sports 

 arose independently in the genus Eueides, in which the inner black 

 ^vas absent, is given by '-^^|g^^g|J^, or 13,900 to 1. It is there- 

 fore probable that the five Eueides lacking the inner black are 

 the descendants of a single ancestor. 



(3) Variatio?is of the ''Inner Yellow'' and ''Middle Yellow"" 

 Areas. Tables 3 and 5, and diagram Fig. 98, Plate 9, show the 

 color- variations of the "inner yellow " and " middle yellow " areas 

 in the fore wings of the Danaoid Heliconidae. These areas are 

 marked III and V, respectively, in the figm-es upon Plate 4. The 

 "inner yeUow" area, it will be remembered, occupies the outer por- 

 tion of the cell of the fore wing; while the "middle yellow" is found 

 in the region just beyond the outer limits of the celf. The two areas 

 are often fused together as in Figs. 47, 48, 50, 51, and 55, Plate 4. 

 The inner yellow area is usually smaller than the middle yellow, 

 and a comparison of Tables 3 and 5 will show that it is much more 

 frequently obliterated by the encroachment of the rufous or black 



