182 Oh the Geographical Distrlbulion of Insects. 



but moderately rich in species, sucli as the genus Calosoma, 

 which contains scarcely more than thirty, sixteen of which are 

 allotted to America, ranging fi-om the Arctic Regions to Terra 

 del Fuego, and fourteen to Africa, Europe, Siberia, China, and 

 New Holland, where they are scattered about often at immense 

 distances from each other. Among the richest, there is one 

 iCicindeld) which covers the whole globe with its species ; but 

 these, although more abundant in Avarm countries, are pretty 

 equally spread, and our climates possess a considerable pro- 

 portion ; their area is likewise continuous, except in the case 

 of the two continents. Other genera shew a very diiferent 

 mode of distribution, as for example the genus Carabus. Its 

 species, as is well known, are concentrated in the same zone 

 as the family, and in the Old Continent they cease at the foot 

 of the Atlas and the coasts of Asia Minor, In the New Con- 

 tinent, on the contrary, we find fifteen concentrated in Canada 

 and the North of the United States ; then a single one (C. 

 Chilensis, Eschs.) in the south of Chili ; and, finally, another 

 C. Basilicus, Chev.*), among the Antilles, at Porto Rico, where 

 it was lately discovered. This genus likewise presents, in an 

 eminent degree, a triple example of sporadicity, of the dis- 

 junction of areas, and of species insulated from their groups. 

 Finally, there are numerous other genera of the same family, 

 which ai'e peculiar to coimtries, and even localities, of a very 

 limited extent. 



It is useless to enter into analogous details in relation to 

 species ; it is obvious that their geograjihical extension in 

 general is inferior to that of genera, although in other re- 

 spects they repeat, as to continuity and disjunction of areas, 

 what is observed in the preceding gi'oups. 



The distance of regions from each other likewise produces 

 general results, which it is necessary to take into account. 



When two regions which resemble each other are at the same 

 time contiguous, their species are almost wholly alike ; this is 

 witnessed, for example, in France and Germany. If these 

 regions are separated by a considerable interval, their species 

 are for the most part diflFerent, but the genera remain the 



* Magazin de Zoologie dc Gnerin, Inscctes, pL 109. 



