HIMALAYAS AND OF INDIA. XXXIX 
Insects and times of their appearance, the soil in which they are found, and the vegetation upon which they 
live; since the distribution of anifhals in general is greatly dependent on food, which food will abound, 
or be found deficient, according to the richness or poverty of the soil, or according as the degrees of 
heat and moisture influence the same. It appears to me, that it is chiefly in swamps, and in low 
and marshy lands acted on by the rays of the sun, where there is a union of heat and moisture, that the 
major part of Insects seem particularly to flourish. In such localities we find genera more abundant, 
a great increase of species, the number of individuals prodigiously augmented, and the energies of life 
more rapidly developed. Animals appear more than usually productive, either in the alluvium of 
mighty rivers, or in the tropical jungle. It was on the banks of the Nile, amid its slime, acted on by 
the influence of the sun, that the doctrine of spontaneous generation originated, and I am told also enter- 
tained by the ancient Brahmans on the banks of the Ganges, as seen in Susruta. It is in like situations, 
where heat and moisture predominate, that nature still exhibits her surpassing and inexhaustible fecundity. 
_ If we next turn our attention to the tropical jungle, we meet there with nearly an equally teeming 
exuberance and productiveness of species. ‘The heavy tropical rains saturating the accumulated mass of 
heated leaves, and vegetable matter, considerable vapour is produced peculiarly adapted to increase 
insect life; and it is not a little singular, that as soon as the first showers fall in these regions, all nature 
becomes reanimate ; and as the rains increase, so do the Insects in proportion more and more, till the 
rainy season fairly sets in, at which period the jungle and the forest literally teem with myriads of 
insect population, more numerous than the stars of heaven, and as countless as the sands of the sea- 
shore. In concluding this part of my subject, I need only repeat shortly, that heat and moisture 
combined, exercise a powerful control over the geographical distribution of insect life, and that this 
distribution is also inflenced in a greater or less degree by vegetation, as well as jodie the soil of a 
country ; but these are subjects which require further elucidation. 
INFLUENCE OF VEGETATION. 
‘The entomologist who wishes for accurate information respecting the geographical distribution of 
Insects over the wide extent of our globe, must take into his consideration not only the influence of 
temperature, but that of vegetation; nor should he omit to note the varieties of soil which materially 
influence it. The dependence of this distribution of animals, although greatly swayed by temperature, 
is no less so by the supply of food and nourishment they can obtain. Insects are designated 
according to the kind of food they consume, as carnivorous or phytyvorous; and in proportion as food 
is ample or deficient, so probably they abound in numbers, or decrease and. vary in magnitude and 
form. 'To its abundance we may in some measure attribute size, to its deficiency the frequency of 
dwarfishness of stature, immaturity, and many of the numerous crippled specimens, as also some of 
the monstrosities found in our collections. The great Latreille has justly observed, that where the 
empire of Flora ends, there also terminates that of Zoology; and I have little doubt, that where 
vegetation is richest, there animal groups also will be found most ee Ae La I 
individuals, not only those which are herbivorous, but those also which are carnivorous, — 
It is not my intention here to enter into any details respecting the Himalayan or Indian Flora. If 
the reader requires information on these points, I refer him at once to the accurate and invaluable pages 
cof Dr. Wallich and Dr. Royle; and as I at present look merely to the vegetation, as influencing in a | 
great measure the character of the entomology of the country, a concise outline of the leading features of 
the Botany of those regions is all that is here requisite. Throughout India, according to the above 
authorities, there appears to be an uniformity of vegetation, tropical species greatly predominating over 
those of the temperate zones; there occurs also a considerable admixture of genera belonging to 
temperate climes, and at a high elevation plants abound, which are indicative of Alpine regions. Several 
f2 genera 
* 
