292 INDIRECT BENEFITS DERIVED FROM INSECTS- 



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 lately published an ingenious paper 

 on the subject", 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 Apocr/nmn androscBmifolium, 

 Asclepias st/riaca and curassavica, Nerium Oleander, 

 and a grass described by Michaux under the_narae of 

 Leersia lenticularis . The second class includes those 

 which entrap them by some viscosity of the plant, as 

 many species o^ Rhododendron^ Kalmia, Robinia, Silene, 

 Li/thrum, Populus balsamifera, &c.^ And under the 

 third class will arrange those which ensnare by their 

 leaves, whether from some irritability in them, as in 

 DioncEciy Drosera, &c., or merely from their forming 

 hollow vessels containing water, into Avhich 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, Aquarium^ &c., the tubular 

 leaves of which are usually found stored with putrefying 

 insects. In this last class may be placed the common 

 Dipsacus 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 



' Philosoph. Mag. xxxix. 107. 



" Small flies are sometimes found sticking to the glutinous stigma of 

 some of the Orchidese like birds on a limed twig: (Sprengel Entdecktes 

 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, ^nn. of Bot. ii. 590. 



