( &/) 
effects of the orange, yellow and green parts of the spectrum. 
The predominance of rays from this region in the light 
incident upon the larva before pupation hindered the formation 
of dark pigment, and tended towards the production of green 
varieties of the pupa. But it was very remarkable that the 
orange and yellow light produced stronger effects in both 
these directions than the green itself. It seemed probable 
that the explanation might be found in the theory that the 
orange and yellow rays existing in the impure mixed greens 
found in Nature were the really efficient stimuli which pro- 
duced effects of protective resemblance to the green colour 
itself. Mr. Poulton said he had suggested this explanation when 
he published the account of his experiments; but it was very 
satisfactory to find the explanation further supported by Mr. 
Griffiths’ facts. Mr. Griffiths’ yellow paper also produced 
much stronger effects than the green paper used by him. 
The extremely sensitive nature of the larve before pupation 
was shown by the marked effects following from the pale 
tissue paper used by Mr. Griffiths. In his (Mr. Poulton’s) 
experiments much stronger colours were employed, so that the 
test of larval susceptibility was not nearly so severe. 
Mr. Poulton further said that as we now know that the 
colour-influence is efficient for many hours of the period 
before pupation, and that it probably ceases for most of the 
third stage when the larva is motionless and fixed by the 
silken girdle and anal pad, it is clear that Mr. Griffiths’ 
experiments with particoloured surroundings did not afford 
any true test of the effects of such a stimulus; for his 
colours were applied during the third stage only, and without 
special care to ensure their application as early as possible in 
the period. In view of statements about parti-coloured pupx 
found upon red brick and grey mortar, and considering Mr. 
Barker’s observation of a parti-coloured pupa of Papilio niveus 
supposed to result from the effects of brick and wood, it would 
be well to test the Pieride thoroughly with two colours pro- 
ducing as opposite an effect as possible. Black and orange 
would be the best colours for the purpose, and a box might 
be lined with a small chess-board pattern of those colours, 
the squares being so small that a larva would be compelled 
PROC, ENT. SOC. LOND., 1., 1888. Gn 
