The inheritance of Wing-Colour in lepidoptera

Conclusions

• 1. It is contended that the evidence advanced by Cockayne is not sufficient to deny segregation in the Mendelian sense, in crosses betweenD. mendica and its white varietyrustica.

• 2. The experiments reported show that in theF ₁ generation the males are not much deeper in colour than “purerustica,” so that this form may be considered dominant to a great extent over the type; in fact, some heterozygous insects are indistinguishable fromrustica.

• 3. The great variation in the buff coloured hybrids is probably due to the effects of modifying genes. The colour of these buff insects as well as that of the others was measured in the tintometer. The construction of distribution curves in the manner previously described enables the segregation of these variable insects to be followed without difficulty.

• 4. Segregation is found to take place in theF ₂ generation, the purerustica and the black type males segregating from the heterozygous buff coloured insects in an approximately 1:2:1 ratio. Owing to the fact that some heterozygous males are indistinguishable from purerustica, the latter class is found to be too numerous.

• 5. The crosses between theF ₁ generation and type individuals also show very clear segregation in the males, there being equal numbers of type, and buff coloured or white insects.

• 6. The statement that var.rustica is phylogenetically the older race is supported by a consideration of what is known concerning the chemistry of black pigments.