36 
[January, 
The Action of Light upon the 
how the reds of ladybirds, of Aphodius fimetarius, of Elater 
sanguineus , &c., lose their purity and brightness on exposure, 
and to some extent even on preservation in darkness. Even 
darker and more intense colours are gradually affeCted. 
Thus in the collection of native beetles in the British 
Museum, which have doubtless been exposed to the light for 
some years, the jet-black Typhceus vulgaris — absurdly known 
as the “bull-comber ” — has taken a decided chestnut-brown, 
whilst a similar change has come over the blue-black elytra 
of the common dung-beetle. 
To test the speed of the bleaching power of light upon 
deep-coloured Coleoptera we placed in a glass case, outside 
a south-western window, specimens of the following spe- 
cies : — Cetonia aurata, Eupcecilia Australasia, Typhceus vul- 
garis, Geotrupes stercorarius, Ahax striola, and Sternocera 
orientalis, — and exposed them to the sun during the months 
of June, July, and August, 1876. The Cetonia and the 
Sternocera , whose colours are of the interference-class, were 
unaffected ; but the black of the Typhceus, the Geotrupes, and 
the Ahax was changed to a brown, and the brown of the 
Eupcecilia to a very dirty yellow. Thus we see that even 
the darkest and most intense pigment- or absorption-colours 
are affeCted by light. This faCt accounts for one class of the 
variations in colour met with in different specimens of one 
and the same species. An inseCt that has lived long and 
has been much exposed to the sun may have more degraded 
colours than such as are captured soon after reaching full 
perfection. 
If we examine the nature of the changes produced by the 
aCtion of light we shall notice the following faCts : — Pigment 
greens, blues, lilacs, pinks, and roses — shades not very 
abundant in the animal kingdom — are the first to fade. 
Full reds, purples, and blacks resist longer. Oranges, yel- 
lows, fawns, drabs, browns, and olives have still greater 
permanence, merely taking a duller or dirtier tone. The 
changes ensue in a definite direction. Blues and pale greens 
turn to a grey or a yellowish drab ; darker greens to an olive ; 
lilacs, pinks, and roses to various shades of grey ; reds be- 
come a reddish or yellowish brown ; purples a very dirty 
brown ; yellows and oranges verge more to a pale brown, 
and may rank as buffs or fawns. The alteration is therefore 
from the primary or secondary towards the tertiary colours, 
accompanied with a decrease in depth. But we have never 
seen a primary colour, when fading under the influence of 
light, pass into another primary colour ; nor does any 
secondary or tertiary colour ever pass into a primary. The 
