42 The Action of Light upon the [January, 
at (Eningen and elsewhere (See “ Quarterly Journal of 
Science,” vii., 255), that certain groups, now mainly tropical 
or subtropical, were very extensively developed in Central 
Europe ; but at the same time we find indications that the 
climate, at least as far as warmth is concerned, was almost 
tropical in its character. 
We may next inquire whether the relative brilliance of 
colour in various animal groups is at all connected with 
their diurnal or nocturnal habits, or with their greater or 
less exposure to light at different stages of their develop- 
ment. It is a truism that the diurnal Lepidoptera are upon 
the average much more highly coloured than the nocturnal 
species, the moths. Some weight has been laid on the 
circumstance that in butterflies both sides of the wings are 
freely exposed to light, and that both are also adorned with 
a variety of hues, whilst in moths, where the under surface 
of the wings is not turned to the light, it generally exhibits 
a dull and uniform colouration ; but these fadts admit of 
much qualification. Even among the small number of 
beetles indigenous in Britain there are some — such as 
Erehia Cassiope, Ccenonymphci Davus, and Thanaos Tages 
certainly less brightly coloured than many moths. Many 
species of butterflies, also, if richly coloured on the upper 
surface of the wings, can boast no gay or varied tints be- 
neath. We need only mention the common peacock 
(Vanessa Io ). Again, in certain genera of moths we find 
colours as vivid as can be met with in butterflies — e.g., 
Callimovpha, Euchelia, Chelonia , and Catocala. The most 
remarkable feature in these genera is that the chief display 
of colour appears on the upper surface of the hind wings — 
a part as little exposed to light as the lower surface, since 
when the insedt is at rest, in the daytime, it is completely 
screened by the anterior pair of wings. 
In the larva state it cannot be said that Lepidopterous 
insedts are much exposed to light. As a rule the caterpillars 
of the diurnal as well as of the nodturnal species prefer 
shade to sunshine. It is perhaps somewhat curious that 
the habits of the larva stand in no regular connedtion with 
the diurnal or nodturnal charadter of the mature insedt. 
Turning to the Coleoptera, we find further facts unfa- 
vourable to the supposed predominant influence of light 
upon the development of colour. Such Coleopterous larvae 
— and they are the majority — as live in total darkness are, 
indeed, generally of a dull dirty grey, contrasting strongly 
with caterpillars which are more or less exposed to light, 
and many of which exhibit a bright and pleasing colouration. 
