INDIRECT BENEFITS DERIVED FROM INSECTS. 293 



the pupae of Lepidoptera, as Mr. White tells us, are the 

 grand support of those that have a soft bill a . 



I shall close my list of the indirect benefits derived 

 from insects, by adverting 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 Muscicapae, 

 which have been enumerated by Dr. Barton of Phila- 

 delphia, who has published an ingenious paper on the 

 subject 5 , 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 androscemifolium^ Asclepias syriaca and 

 curassavica, Nerium Oleander, and a grass described by 

 Michaux under the name of Leersia lenticular is. The 

 second class includes those which entrap them by some 

 viscosity of the plant, as many species of Rhododendron, 

 Kalmia, Robinia, Silene, Lythrum., Populus balsamifera, 

 &c. c And under the third class will arrange those which 

 ensnare by their leaves, whether from some irritability in 

 them, as in Dion&a, 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, 



a White's Selborne, i. 181. b Philos. Mag. xxxix. 107. 



c Small flies are sometimes found sticking to the glutinous stigma 

 of some of the Orchideas like birds on a limed twig: (Sprengel Ent- 

 decktes Geheimniss, 21 ) and ants are 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. of Sot. 

 ii. 390. 



