1^(1 M. Liitreille ofiilie Geographical Distrihutmi of Insects. 
it as well as possible, to divide it according to some fixed prin- 
ciples, into parts which were in harmony with my observations, 
so that the blanks or squares might be filled up, in proportion as 
the objects which ought to be there placed should be discovered. 
I have proposed to myself, in a Word, to make geography ac- 
cord with entomology in a general manner, not susceptible of ex- 
treme rigour. For the rest, it is, as I have already said, an at- 
tempt which has need of renewed consideration. 
The progressive increase in the intensity and duration of heat, 
has an influence on the size, the developement of the mucous 
membrane, and the colours of insects. In general, the nearer 
we approach the equinoctial regions, the more we find species re- 
markable for their size, the eminences and inequalities of their 
bodies, the brilliancy and variety of their colours. I believe 
I may assert, that the augmentation of light tends to convert 
the yellows into red or orange, and that its diminution causes 
them to pass into white. The same observation applies also to 
shells. The Heli-x nemoralis^ which, in our climate, has a yel- 
low ground or base, is red or reddish in Spain. When, in pro- 
ceeding from north to south, we arrive at the island of Tenerifle, 
we there perceive that our cabbage-butterfly {Papilio cheira7bthi^ 
Hiibn.), and that which we name Vulcan {atalanta)^ have ex- 
perienced a modification of their colours. The diurnal butter- 
flies of our mountains have, for the most part, the base of the 
wings white or brown, more or less deep. 
These observations on the climates of insects, &c. interest the 
geographer not less than the naturalist. They may prove use- 
ful in the determination of the natural limits of some disputed 
countries, as in the q^se of islands situated between two con- 
tinents, the respective distance of which may be too great to 
enable animals and vegetables to be propagated from the one to 
the other. We have seen that Greenland, which geographers 
join to America, is, according to the Fauna of Fabricius, more 
allied to Europe, or at least, that it may be regarded as a middle 
land, to which either continent may lay claim. Thus, the Ca- 
nary Islands and Madeira, ought to be associated to Africa, for 
the insects found there are perfectly analogous to those of Bar- 
bary and the adjacent countries. America, also, differs under 
