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. When 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 pupae of Lepidoptera, 

 as Mr. White tells us, are the grand support of those that have a soft 

 bill, i 



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 Muscicaptz, which have been enumerated by Dr. 

 Barton of Philadelphia, who has published an ingenious paper on the sub- 

 ject 2 , 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 androsfsmifolium, 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, Ly thrum, Populus balsamifera, &c. 3 And 

 under the third class will arrange those which ensnare by their leaves, 

 whether from some irritability in them, as in Dioncea, 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- 

 rium, 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 Muscicapa asclepiadea: that has not 

 entrapped its victim, and some of them in the United States closely cover 

 hundreds of acres together. 



i White's Selborne, i. 18L 8 Philos. Mag. xxxix. 107. 



5 Small flies are sometimes found sticking to the glutinous stigma of some of the 

 Orchideae like birds on a limed twig (Sprengel, Entdecktes Geheimniss, 21.) ; and 

 ants ai-e not unfrequently detained in the milky juice which the touch of even their 

 light feet causes to exude from the calyxes of the common garden lettuce. Ann, 

 ofBot. ii. 590. 



M 4 



