346 On the Geographical Distribution of Insects. 



ly proves the proposition stated above. With regard to the 

 other orders not included in it, every thing leads us to believe 

 that they will shew a similar result, and that their progression 

 from the poles to the equator will be, in regard to some of 

 them, even more decided. Thus the whole of Europe and Si- 

 beria possess not more than 260 diurnal Lepidoptera, while 

 the explored parts of Brazil, which do not nearly equal them 

 in extent, have already furnished upwards of 600. The same 

 country is an inexhaustible mine for Hymenoptera and He- 

 miptera ; but our temperate regions, perhaps, present a less 

 striking inferiority in Orthoptera, Neiu'optera, and Diptera. 



Genera are so vaguely determined in the present state of 

 entomology, that a less satisfactory calculation can be made 

 with regard to them. The number of them in a given country 

 is not without importance, for it is they rather than the spe- 

 cies which give to a country its proper entomological physiog- 

 nomy. The following table is drawn up from De Jean's Ca- 

 talogue, a work in which the generic groups are extremely nu- 

 merous. 



Country 



Siberia, . . . 

 Europe, . . . 

 North America, 

 South America, 

 Africa, . . . 

 New Holland, . 



Species. 



465 

 5,677 

 2,403 

 8,112 

 2,942 



320 



169 

 715 

 541 

 1209 

 674 

 162 



No. of Species, 

 per Genus. 



2.7 

 7.9 

 4.4 

 6.7 

 4.3 

 2. 



From this it follows, that the absolute number of genera 

 augments from the north to the south, since Europe has more 

 than Siberia, and South America more than Europe ; but it 

 will be seen, at the same time, that this number does not in- 

 crease in the same proportion as the species, but that it fol- 

 lows, on the contrary, an inverse progression. In reality, all 

 the families, Avith a very small number of exceptions, have re- 

 presentatives in all the great regions of the globe ; each of 

 them will, consequently, include a smaller number of insects 

 in proportion to the entomological poverty of these regions. 

 The genera constituting these families have, in their turn, for 

 the most part, their representatives or analogues in the same 



