ciiAi\ XXI.] INSECTS. 499 



9; and in this respect the Xeotropieal region agrees with them, 

 though the superiority in the proportion of Cerambycidte is 

 somewhat less. In the Old World tropical regions, however, 

 and in Australia, the Lamiidse greatly preponderate — beinf 

 nearly double in the Oriental and Ethiopian regions (or as 11 to 

 6), while in the Australian it is as 6 to 5. The I'rionidas show 

 a similar difterence, though in a less degree ; being proportion- 

 ately more numerous in the North Temperate and Neotropical 

 regions. Now, as regards tlie North Temperate regions, this 

 ditference can be, to some extent explained, by a difference in 

 the habits of the insects. The Lamiidie, which both in 

 the larva and perfect state have exceedingly powerful jaws, 

 exclusively frequent timber trees, and almost always such as 

 are dead ; while the Cerambycidie, are generally more delicate 

 and have weaker mandibles, and many of the species live on 

 shrubs, dead twigs, foliage, and even on flowers. The immense 

 superiority of the Tropics in the number and variety of their 

 timber trees, and the extent of their forests, sufficiently accounts 

 for their superiority to the Temperate regions in the develop- 

 ment of Lamiida3 ; but the great excess of Cerambycidte in 

 South America as compared with the rest of tlie Tropics, is not 

 to be so readily explained. 



Bearing in mind the different proportions of the families, as 

 above noted, we may now consider the distribution of the 

 Longicorns as a v.hole. In numl)er of generic forms, tlie Neo- 

 tropical region, as in so many other groups, has a marked 

 superiority. It possesses 51(3 genera, 489 of which (or about 

 l^ of the whole) are peculiar to it. The Australian and Orien- 

 tal regions come next, and are exactly equal, both possessing 

 3(]0 genera, and having almost exactly the same proportion (in 

 each case a little less than f ) peculiar. The Etliiopian region 

 has 262 genera, with alxmt f peculiar; the Pahearctic 190, witli 

 51 (rather more than |) peculiar; and the Nearctic 111, with 

 59 (a little more than half) peculiar. The more isolated of 

 the sub-regions are also well characterised by peculiar genera. 

 Thus, Chili with Temperate South America possesses 37, a 

 large proportion being Cerambycida> : the Malagasi group 26, 



K K 2 



