330 THE AMERICAN NATURALIST [Vol. XLVHI 



ent in marked degree, is dominant over the narrower 

 margin in philodice. This dominance of the orange mani- 

 fests itself quite as distinctly if the albino female of 

 eurytheme, instead of the orange female, is bred to the 

 yellow philodice male. The daughters of such a family 

 in one case (0, 1913) were 36 white, 35 orange; the sons, 

 numbering 72, were, of course, all orange. The white 

 species-hybrid (F x ) is identical in appearance with the 

 albino eurytheme, the female color pattern of the latter 

 (wide marginal bands) being dominant, and the orange 

 middle spot both in pure bred albino eurytheme and in 

 the albino hybrid being usually paler than in their orange 

 sisters. 



The second hybrid generation inbred (F 2 ) shows a well 

 marked segregation of the sulphur-yellow color of philo- 

 dice, as a simple Mendelian recessive. Three out of the 

 sixteen colored (non-albino) individuals of the brood ob- 

 tained in December, 1913, are definite recessives of clear 

 sulphur yellow, with pale yellow middle spots on the hind 

 wing. The most highly colored individuals are four that 

 correspond in hue to pale examples of the light orange- 

 yellow winter variety, ariadne. There is no return, at 

 least in this winter brood (enclosed in a greenhouse in 

 New Hampshire in December), to the brilliant orange of 

 the grandparental eurytheme stock. Nor do they even 

 return to the suffused light orange (intermediate) tint 

 of the heterozygous father (keewadin type), for the 

 ground color of all individuals of this brood (F e ) is 

 yellow, either flushed or spotted, except in three indi- 

 viduals, with orange. 



An interesting case of probable hybridization in the 

 allied genus Meganostoma, or dog's head butterfly, is re- 

 corded by Wright 9 between the Californian M. eurydice 

 and M. cccsonia, common throughout the southern states. 

 The two species are remarkably different in color and 

 have different food plants. The male of eurydice differs 

 from that of cccsonia in having a violet luster and lacking 



»Loc. ext., p. 136. 



