M. Latreille on the Geographical Distribution of Insects. 37$ 
throw over them so much uncertainty, considering the difficulty 
which there is in appreciating the importance of the modifying 
circumstances, whether single or combined. 
I shall consider the climates under another point of view, that 
which is offered us by the genera of Arachnides * and of Insects, 
peculiar to determinate spaces on the surface of the earth. Our 
catalogues relating to exotic species , are too imperfect to admit 
of our following another plan ; for even the European entomo- 
logy may be said to be nothing more than sketched *f*. But, 
even supposing that we had not to plead this penury of mate- 
rials, I would not fatigue, by the wearisome enumeration of spe- 
cies, and by all the little details into which the subject would 
conduct us. Would it not be necessary always to fix one’s 
attention on some general ideas, and on the most important 
results ? Such is the end which I have proposed to myself ; 
and although, with more assistance, I might have succeeded 
better, I trust, however, that a good use of the feeble means 
which my studies have furnished me, will lead to new views 
which I believe worthy of interest. For the rest, I may be 
said to open a new path, or rather to mark out its traces, and 
my efforts, even though fruitless, may at least merit some in- 
dulgence. 
Many of our travelling naturalists may be reproached with 
negligence in regard to their indication of the precise places 
where they collected the objects which enrich our museums. 
This first fault committed, one need not be surprised that they 
have not remarked the particular qualities of the soil, considered 
physically, and under its mineral ogicai aspects. Yet these de- 
tails form an essential part of the history of animals. The 
genus Licinus , the Papilio cleopatra , many of the genus D asp- 
ics, ( Dermestes , Lin.) some species of Lamia, &c. are only 
found on calcareous soils. I have observed that the Pimelia 
bipunctuata , very common in the environs of Marseilles, scarce- 
ly extends to the sea-coast. If the interior of lands in Bar- 
* The class Arachnides consists of the genera Aranea , Scorpio , A cams, &c, 
recently removed from the Insecta. They arc remarkable for the want of an- 
tennae, and distinguishable from the true insects by other important characters. 
f Even with all the talents of M. de Humboldt, it would he impossible to do 
for the geography of Insects, that which he has executed for the geography of 
Plants, 
