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THE AMERICAN NATURALIST [Vol. XLVIII 



scribed by Nabours. 6 These nine color types, or species, 

 freely interbreed. The color pattern of the resulting F t 

 hybrid in each case is a mosaic combination of those of 

 the two parents. The latter in subsequent inbreeding 

 may be extracted intact, each having been transmitted as 

 a distinct unit, without dominance. 



In Lepidoptera, an order in which polymorphism is 

 notoriously common, hybridization between species has 

 been frequently observed. Standfuss 7 devotes eight 

 octavo pages of his excellent " Handbuch " simply to the 

 enumeration of examples of such hybridization between 

 palaearctic species of moths and butterflies, and acknowl- 

 edges that he mentions only a fragment of all such cases 

 on record or preserved in collections. This list would be 

 greatly extended if American species were included. 

 Seven different hybrid combinations within the genus 

 Colias in the palaearctic region have been noted by Stand- 

 fuss. 



Golias philodice, the clouded sulphur or clover butterfly 

 of the eastern and central United States, readily crosses 

 with C. eurytheme, the orange sulphur or alfalfa butterfly 

 of the western and central states. The territory of philo- 

 dice, according to Scudder extends like a wedge westward 

 from the Atlantic into the faunal area of eurytheme. 

 Overlapping thus occurs in the Mississippi Valley, though 

 philodice does not extend as far southward as the Gulf 

 States, Texas, Louisiana and Mississippi, in which 

 eurytheme is found. 



These two species are fairly sharply distinguished by 

 the difference in the ground color, which in eurytheme is 

 orange, in philodice sulphur yellow. The middle spot of 

 the upper side of the hind wing is brilliant orange in 

 eurytheme, pale orange or yellow in philodice. The dark 

 border of the hind wing of the female is wider in eury- 

 theme than in philodice and broken with a row of large 

 yellow spots. 



e Journal of Genetics, Vol. 3, No. 3, February, 1914. 



t "Handbuch d. palliarktischen Gross-Schmetterlinge," 1896, p. 51-53. 



