VII 
THE COLOURS OF THE LEPIDOPTERA 
149 
microscope a wonderful play of colours which is 
quite invisible to the naked eye. He suggests 
reasonably enough that it is in no respect im¬ 
probable that these colours may be visible to other 
insects although not to us except by the aid of 
optical instruments, and that therefore they may 
quite alter the appearance of the insects as seen by 
other butterflies. Such observations are of interest 
as tending to exercise a check upon the purely sub¬ 
jective treatment of questions of colour-resemblance. 
The Pigments of the Pieridae 
As an introduction to the discussion of the pig¬ 
ments of butterflies we may take Mr. F. Gowland 
Hopkins’s laboriously patient work on The Pigments 
of the Pier idee. 
The Pieridae include a large number of butterflies, 
among which the most familiar are our common 
Cabbage Butterflies or Garden Whites; they are 
very widely distributed, and are said to exhibit in 
a striking manner the phenomena of mimicry. In 
America especially they are said to mimic very 
closely the (by hypothesis) well-protected Heliconidae. 
The Pieridae exhibit a relatively simple plan of colora¬ 
tion ; optical colours are absent or little developed ; 
and we shall see later that this greatly limits the 
possible colouring. In fact we find that the colours 
are mainly white, yellow, and black. The yellow, 
in accordance with a rule which is exceedingly pre¬ 
valent among butterflies, may deepen into orange or 
red, this occurring most frequently in species from 
