298 INDIRECT BENEFITS DERIVED FROM INSECTS. 



impregnate the stigma ; but this important affair is de- 

 volved upon a particular species of gnat (Cecidomyia 

 pennicornis). The throat of the flower is lined with dense 

 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 re- 

 turn : several creep in, and, uneasy at their confinement, 

 are constantly moving to and fro, and so deposit the 

 pollen upon the stigma : but when the work entrusted to 

 them is completed, and impregnation has taken place, 

 the hair which prevented their escape shrinks, and ad- 

 heres closely to the sides of the flower, and these little 

 go-betweens of Flora at length leave their prison 3 . 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 fructify- 

 ing the plants of the Linnean classes Monoecia, Dioecia 

 and Polygamict) 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 be- 

 sides bees b , 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 



a Grundriss der Kr'duterkunde, 353. A writer however in the An- 

 nual Medical Review (ii. 400.) doubts the accuracy cf this fact, oil the 

 ground that he could never find C. pennicornis y though A. Clematitis 

 has produced fruit two years at Brompton. Meigen (Dipt. i. 100. e.) 

 places this amongst his doubtful Ceddomyice. Fabricius considers 

 it as a Chironomus. 



b I have frequently observed Dermestesflavesccns, Ent. Brit. (By- 

 turus) eat both the petals and stamens of Stellaria Holosteum; and 

 MordellfB will open the anthers with the securiform joints of their 

 palpi to get at the pollen. 



