As the letter I wrote in reply is lost, and as it is rather difficult to explain the matter clearly without reference to the coloured figures, I must go into some little detail, and give now what was probably the explanation I gave at the time.

The male of Papilio Memnon is a large black butterfly with the nervures towards the margins of the wings bordered with bluish gray dots.

It is a forest insect, and the very dark colour renders it conspicuous; but it is a strong flier, and thus survives.

To the female, however, this conspicuous mass of colour would be dangerous, owing to her slower flight, and the necessity for continually resting while depositing her eggs on the leaves of the food-plant of the larva.

She has accordingly acquired lighter and more varied tints.