168 INDIRECT BENEFITS DERIVED FROM INSECTS. 
What may be the precise use of this faculty is not so apparent. Dr. 
Barton doubts whether the flowers that catch insects, being only tempo- 
rary organs, can derive any nutriment from them ; and he does not think it 
probable that the leaves of Dionea, &c., which are usually found in rich 
boggy soil, can have any need of additional stimulus. As nothing, how- 
ever, is made in vain, there can be little doubt that these ensnared insects 
are subservient to some important purpose in the economy of the plants 
which are endowed with the faculty of taking them, though we may be 
ignorant what that purpose is; and an experiment of Mr. Knight’s, nur- 
seryman in King’s Road, London, seems to prove that, in the case of 
Dionea at least, the very end in view, contrary to Dr. Barton’s supposi- 
tion, is the supplying the leaves with animal manure ; for he found that 
a plant upon whose leaves he laid fine filaments of raw beef was much 
more luxuriant in its growth than others not so treated.’ Possibly the 
air evolved from the putrefying insects with which Sarracenia purpurea is 
sometimes so filled as to scent the atmosphere round it, may be in a similar 
manner favourable to its vegetation. 
Most of the insects which are found in the tubular leaves of this and 
similar plants enter into them voluntarily; but Sir James Smith mentions 
a curious fact, from which it appears that in some cases they are deposited 
by other species. One of.the gardeners of the Liverpool Botanic Garden 
observed an insect, from the description one of the Crabronide, which 
dragged several large flies to the Sarracenia adunca, and haying with some 
difficulty forced them under the lid or cover of its leaf, deposited them in 
its tubular part, which was half filled with water ; and on examination all 
the leaves were found crowded with dead or drowning flies.» What was 
the object of this singular manceuvre does not seem very obvious. At the 
first glance one might suppose that, having deposited an egg in the fly, it 
intended to avail itself of the tube of the leaf instead of a burrow. Yet 
we know of no such strange deviation from natural instinct, which would 
be the more remarkable, because the insect was Huropean, while the plant 
was American, and growing in a hot-house. And, at any rate it does not 
seem very likely that the insect would commit her egg to the tube without 
having previously examined it ; in which case she must have discovered it 
to be half full of water, and consequently unfit for her purpose. It is not 
so wonderful that many large flies should, as Professor Barton informs us, 
drop their eggs into the Ascidia furnished with dead carcasses ; and it 
seems very probable that Dytisci oviposit in them ; for the Squil/a, which 
Rumphius found there, was probably one of their larva, this being the 
old name for them. 
However problematical the agency of insects caught by plants as to their 
nutriment, there can be no doubt that many species perform an important 
function with regard to their impregnation, which indeed without their aid 
would in some cases never take place at all. Thus, for the due fertilisation of 
the common Barberry (Berberis vulgaris), it is necessary that the irritable 
stamens should be brought into contact with the pistil by the application 
of some stimulus to the base of the filament ; but this would never take 
place were not insects attracted by the melliferous glands of the flower to 
1 Plements of the Science of Botany, 62. 
2 Smith’s Introduction to Botany, 195 
5 Mouffet, 319, 
