CHAP.' XXI.] 
INSECTS. 
499 
9; and in this respect the Neotropical region agrees with them, 
though the superiority in the proportion of Cerambycidae is 
somewhat less. In the Old World tropical regions, however, 
and in Australia, the Lamiidse greatly preponderate — being 
nearly double in the Oriental and Ethiopian regions (or as 11 to 
6), while in the Australian it is as 6 to 5. The Prionidae show 
a similar difference, though in a less degree ; being proportion- 
ately more numerous in the North Temperate and Neotropical 
regions. Now, as regards the North Temperate regions, this 
difference can be, to some extent explained, by a difference in 
the habits of the insects. The Lamiidae, 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 Cerambycidae, 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 Lamiidse; but the great excess of Cerambycidse in 
South America as compared with the rest of the 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 whole. In number of generic forms, the Neo- 
tropical region, as in so many other groups, has a marked 
superiority. It possesses 516 genera, 489 of which (or about 
of the whole) are peculiar to it. The Australian and Orien- 
tal regions come next, and are exactly equal, both possessing 
360 genera, and having almost exactly the same proportion (in 
each case a little less than f) peculiar. The Ethiopian region 
has 262 genera, with about £ peculiar ; the Palsearctic 196, with. 
51 (rather more than J) 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 Cerambycidse; the Malagasi group 26, 
K K 2 
