INDIRECT BENEFITS DERIVED FROM INSECTS. 293 



whose flowers smelling like carrion (Stapelia hirsuta, 

 See.) entice flies to lay their eg-^gs upon them, which 

 thus perish. 



The number of insects thus destroyed is prodigious. 

 It is scarcely possible to find a flower of the Muscicapce 

 Asclepiadece that has not entrapped its victim, and some 

 of them in the United States closely cover hundreds of 

 acres together. 



What may be the precise use of this faculty is not so 

 apparent. Dr. Barton doubts whether the flowers that 

 catch insects, being only temporary organs, can derive 

 any nutriment from them ; and he does not think it pro- 

 bable that the leaves of Dionsea, &c., which are usually 

 found in rich boggy soil, can have any need ofadditional 

 stimulus. As nothing however is made in vain, there 

 can be little doubt that these ensnared insects are sub- 

 servient 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, nurseryman in 

 King's Road, Loudon, seems to prove that in the case 

 of Dionaea, at least, the very end in view, contrary to 

 Dr. Barton's supposition, 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'i?, 's.oxneiixne^ 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 



* Elements nfihe Science of Botany, 62. 



