10 PARA. Cuap. 1. 
Facts of this kind, and there are many of them, would seem to show 
that it is not wholly the external conditions of light, heat, moisture, and 
so forth, which determine the general aspect of the animals of a country. 
It is a notion generally entertained that the superior size and beauty of 
tropical insects and birds are immediately due to the physical conditions 
of a tropical climate, or are in some way directly connected with them. 
I think this notion is an incorrect one, and that there are other causes 
more powerful than climatal conditions which affect the dress of 
species. To test this we ought to compare the members of those 
genera which are common to two regions—say, to Northern Europe and 
equinoctial America—and ascertain which climate produces the largest 
and most beautifully-coloured species. We should thus see the sup- 
posed effects of climate on nearly-allied congeners, that is, creatures 
very similarly organised. In the first family of the order Coleoptera, 
for instance, the tiger-beetles (Cicindelide), there is one genus, 
Cicindela, common to the two regions. The species found in the 
Amazons Valley have precisely the same habits as their English 
brethren, running and flying over sandy soils in the bright sunshine. 
About the same number is found in each of the two countries : but all 
the Amazonian species are far smaller in size and more obscure in 
colour than those inhabiting Northern Europe ; none being at all equal 
in these respects to the common English Cicindela campestris, the 
handsome light-green tiger-beetle, spotted with white, which is familiar 
to country residents of natural history tastes in most parts of England. 
In butterflies I find there are eight genera common to the two regions 
we are thus pitting against each other. Of these, three only (Papilio, 
Pieris and Thecla) are represented by handsomer species in Amazonia 
than in Northern Europe. Three others (Lycena, Melitea and 
Apatura) yield far more beautiful and larger forms in England than in 
the Amazonian plains ; as to the remaining two (Pamphila and Pyrgus) 
there is scarcely any difference. There is another and hitherto neglected 
fact which I would strongly press upon those who are interested in 
these subjects. This is, that it is almost always the ma/es only which 
are beautiful in colours. The brilliant dress is rarely worn by both 
sexes of the same species: if climate has any direct influence in this 
matter, why have not both sexes felt its effects, and why are the males 
of genera living under our gloomy English skies adorned with bright 
colours ? 
The tropics, it is true, have a vastly greater total number of hand- 
some butterflies than the temperate zones; but it must be borne in 
mind that they contain a far greater number of genera and species 
altogether. It holds good in all families that the two sexes of the 
more brilliantly-coloured kinds are seldom equally beautiful; the 
females being often quite obscure in dress. ‘There is a very large 
number of dull-coloured species in tropical countries. The tropics 
have also species in which the contrast between the sexes is greater 
than in any species of temperate zones ; in some cases the males have 
been put in one genus and the females in another, so great is the 
difference between them. There are species of larger size, but at the 
same time there are others of smaller size, in the same families in 
