102 
INFLUENCE OF INSECTS ON VEGETATION. 
with vegetable life as agents of its fecundation, and of its 
destruction.* I am acquainted with no single fact so strik¬ 
ingly illustrative of this importance, as the following statement 
which I take from a notice of Darwin’s volume, On Various 
Contrivances by which British and Foreign Orchids are Fertil¬ 
ized by Insects, in the Saturday Review, of October 18, 1862 : 
“ The net result is, that some six thousand species of orchids 
are absolutely dependent upon the agency of insects for their 
fertilization. That is to say, were those plants unvisited by 
insects, they would all rapidly disappear.” What is true of 
the orchids is more or less true of many other vegetable fam¬ 
ilies. We do not know the limits of this agency, and many 
of the insects habitually regarded as unqualified pests, may 
directly or indirectly perform functions as important to the 
most valuable plants as the services rendered by certain tribes 
to the orchids. I say directly or indirectly, because, besides 
the other arrangements of nature for checking the undue mul¬ 
tiplication of particular species, she has established a police 
among insects themselves, by which some of them keep down 
or promote the increase of others ; for there are insects, as 
well as birds and beasts, of prey. The existence of an insect 
which fertilizes a useful vegetable may depend on that of 
\ 
* I have already remarked that the remains of extant animals are 
rarely, if ever, gathered in sufficient quantities to possess any geographical 
importance by their mere mass; but the decayed exuviae of even the 
smaller and humbler forms of life are sometimes abundant enough to 
exercise a perceptible influence on soil and atmosphere. “ The plain of 
Cumana,” says Humboldt, “ presents a remarkable phenomenon, after 
heavy rains. The moistened earth, when heated by the rays of the sun, 
diffuses the musky odor common in the torrid zone to animals of very 
different classes, to the jaguar, the small species of tiger cat, the cabiai, 
the gallinazo vulture, the crocodile, the viper, and the rattlesnake. The 
gaseous emanations, the vehicles of this aroma, appear to be disengaged in 
proportion as the soil, which contains the remains of an innumerable mul¬ 
titude of reptiles, worms, and insects, begins to be impregnated with 
water. Wherever we stir the earth, we are struck with the mass of 
organic substances which in turn are developed and become transformed 
or decomposed. Nature in these climes seems more active, more prolific, 
and so to speak, more prodigal of life.” 
