INDIRECT BENEFITS DERIVED FROM INSECTS. 295 



its growth than others not so treated a . Possibly the air 

 evolved from the putrefying insects with which Sarracenia 

 purpurea is sometimes 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 

 leaves of this and similar plants enter into them volun- 

 tarily ; but Sir James Smith mentions a curious fact, from 

 which it appears that in some cases they are deposited 

 by other species. One of the gardeners of the Liverpool 

 Botanic Garden observed an insect, from the description 

 one of the Crabronidte, which dragged several large flies 

 to the Sarracenia adwica, and, having with some diffi- 

 culty forced them under the lid or cover of its leaf, de- 

 posited them in its tubular part which was hah filled 

 with water : and on examination all the leaves were 

 found crowded with dead or drowning flies b . What was 

 the object of this singular manoeuvre does not seem very 

 obvious. At the first glance one might suppose that, 

 having deposited an egg in the fly, it intended to avail 

 itself of the tube of the leaf instead of a burrow. Yet we 

 know of no such strange deviation from natural instinct, 

 which would be the more remarkable because the insect 

 was European, while the plant was American and growing 

 in a hot-house. And at any rate it does not seem very 

 likely that the insect would commit her egg to the tube 

 without having previously examined it ; in which case 

 she must have discovered it to be half full of water, and 

 consequently unfit for her purpose. It is not so won- 

 derful that many large flies should, as Professor Barton 

 informs us, drop their eggs into the Ascidia furnished 



a Elements of the Science of Botany, 62. 

 h Smith's Introduction to Botany, 195. 



