Mrs.Barber in South Africa found that the pupae of Papilio Nireus underwent a similar change, being deep green when attached to orange leaves of the same tint, pale yellowish-green when on a branch of the bottle-brush tree whose half-dried leaves were of this colour, and yellowish when attached to the wooden frame of a box.

A few other observers noted similar phenomena, but nothing more was done till Mr.Poulton's elaborate series of experiments with the larvae of several of our common butterflies were the means of clearing up several important points.

He showed that the action of the coloured light did not affect the pupa itself but the larva, and that only for a limited period of time.

After a caterpillar has done feeding it wanders about seeking a suitable place to undergo its transformation.

When this is found it rests quietly for a day or two, spinning the web from which it is to suspend itself; and it is during this period of quiescence, and perhaps also the first hour or two after its suspension, that the action of the surrounding coloured surfaces determines, to a considerable extent, the colour of the pupa.
By the application of various surrounding colours during this period, Mr.Poulton was able to modify the colour of the pupa of the common tortoise-shell butterfly from nearly black to pale, or to a brilliant golden; and that of Pieris rapae from dusky through pinkish to pale green.