INDIRECT BENEFITS DERIVED FROM INSECTS. 297 



hair, pointing downward so as to form a kind of funnel or 

 entrance like that of some kinds of mouse-traps, through 

 which the insects may easily enter but not return : seve- 

 ral creep in, and, uneasy at their confinement, are con- 

 stantly moving to and fro, and so deposit the pollen upon 

 the stigma : but when the work intrusted to them is 

 completed, and impregnation has taken place, the hair 

 which prevented their escape shrinks, and adheres 

 closely to the sides of the flower, and these little go- 

 betweens of Flora at length leave their prison^. Sir 

 James Smith supposes that it is for want of some insect 

 of this kind that Aristolochia Sipho never forms fruit in 

 this country. 



Equally important is the agency of insects in fructi- 

 fying the plants of the Linnean classes Monoecia, Di- 

 oecia and Polygaraia, in which the stamens are in one 

 blossom and the pistil in another. In exploring these 

 for honey and pollen, which last is the food of several 

 insects besides bees'', it becomes involved in the hair, 

 with which in many cases their bodies seem provided 

 for this express purpose, and is conveyed to the germen 

 requiring its fertilizing influence. Sprengel supposes 

 that with this view some plants have particular insects 

 appropriated to them, as to the dioecious nettle Cathe- 

 retes Uriicce, to the toad-flax Catkeretes gravidus^ both 

 minute,beetles, &c. Whether the operations of Ci/nips 



" Grundriss der Krduterkunde, 353. A writer, however, in the Annual 

 Medical Review (ii. 400.) doubts the accuracy of this fact, on the ground 

 that he could never find T- pennicornis, though J. Clematitis has produced 

 frv'.it two years at Broinpton. 



" I have frequently observed Dermestes favescens, Ent. Brit, eat both 

 the petals and stamens of Stellaria Holosteum; and MordelleB will open the 

 anthers with the securiform joints of their palpi to get at the pollen. 



