INDIRECT BENEFITS DERIVED FROM INSECTS. 167 
and waters ; and thus by their flight are regarded as prognosticating fair 
or wet weather. I was one summer much interested and amused by ob- 
serving the tender care and assiduity with which an old swallow supplied 
her young with this kind of food. My attention was called to a young 
brood, that, having left their nest before they were strong enough to take 
wing, were stationed on the lead which covers a bay-window in my 
house. The mother was perpetually going and returning, putting an insect 
into the mouth first of one, then of the others in succession, all fluttering 
and opening their mouths to receive her gift. She was scarcely ever more 
than a minute away, and continued her excursions as long as we had time 
to observe her. hen the little ones were satisfied, they put their heads 
under their wings and went to sleep. The number of insects caught by 
this tribe is inconceivable. But it is not in summer only that birds derive 
their food from the insect tribes: even in winter the pupz of Lepidoptera, 
as Mr. White tells us, are the grand support of those that have a soft 
bill.t : : 
I shall close my list of the indirect benefits derived from insects, by ad- 
verting to the very singular apparent subserviency of some of them to the 
functions of certain vegetables. 
You well know that some plants are gifted with the faculty of catching 
flies, These vegetable Muscicape, which have been enumerated by Dr. 
Barton of Philadelphia, who has published an ingenious paper on the sub- 
ject *, may be divided into three classes : — First, those that entrap insects 
by the irritability of their stamina, which close upon them when touched. 
Under this head come Apocynum androsemifolium, Asclepias syriaca and 
curassavica, Nerium oleander, and a grass described by Michaux under the 
name of Leersia lenticularis. The second class includes those which 
entrap them by some viscosity of the plant, as many species of Rhododen- 
dron, Kalmia, Robinia, Silene, Lythrum, Populus balsamifera, &c. And 
under the third class will arrange those which ensnare by their leaves, 
whether from some irritability in them, as in Dionea, Drosera, &c., or 
merely from their forming hollow vessels containing water into which the 
flies are enticed either by their carrion-like odour, or the sweet fluid which 
many of them secrete near the faux; as in Sarracenia, Nepenthes, Aqua- 
nium, Cephalotus, &c., the tubular leaves of which are usually found stored 
with putrefying insects. In this last class may be placed the common Di- 
psacus of this country, the connate leaves of which form a kind of basin 
round the stem that retains rain-water, in which many insects are drowned. 
To these a fourth class might be added, consisting of those plants whose 
flowers, smelling like carrion (Stapelia hirsuta, &c.), entice flies to lay their 
eggs upon them, which thus perish. 
The number of insects thus destroyed is prodigious. It is scarcely 
Possible to find a flower of the Muscicape asclepiadee that has not 
entrapped its victim, and some of them in the United States closely cover 
hundreds of acres together. 
1 White’s Selborne, i. 181. 2 Philos. Mag. xxxix. 107. 
5 Small flies are sometimes found sticking to the glutinous stigma of some of the 
Orchidew like birds on a limed twig (Sprengel, Wntdecktes Geheimniss, 21.); and 
Ants are not unfrequently detained in the milky juice which the touch of even their 
of Bt re ae to exude from the calyxes of the common garden lettuce—Ann, 
ot. ii, 590, 
uM 4 
