246 NATURAL HISTORY. [cH. XVII. ; 



CHAPTER XVII. 



THE NATURAL HISTORY OP VARIOUS SPECIES OP SAWFLIES. 



An account of the Ovipositor, and Sawing Apparatus An account 

 of the Rose Sawfly Description of their Eggs, Larva, the 

 Effect of Rain Description of their Cocoon their Perfect 

 State its ravages on Turnips. 



OF all the admirably adapted instruments with 

 which insects are furnished to enable them to ac- 

 complish the various ends of their existence, we 

 know of none which can be compared, in the beauty 

 of their construction, to the organs which are em- 

 ployed for the purpose of depositing their eggs by 

 the females of a large family of insects, to which 

 the French have very appropriately given the name 

 of mouches-a-scie, and which we term sawflies ; al- 

 though, as we shall subsequently see, the formation 

 of the organs in question is, as indeed might natu- 

 rally be expected, much more complex and interest- 

 ing in a mechanical point of view, than the tool 

 from which the flies derive their name. 



These insects belong to the same order (Hyme- 

 noptera) as the wasp and the bee, which they some- 

 what resemble ; instead, however, of having the 

 hind part of the body separated from the thorax by 

 a very narrow waist, as we may term it, it is mere- 

 ly a continuation of the body without any visible 

 contraction. Moreover, instead of being provided 

 with a sting like these insects, it is plainly perceiv- 

 ed that that instrument of terror is here replaced 

 by the much more harmless, but not less effective 

 instrument, to which we have already alluded. 



Many of these insects are of a tolerably large 

 size; and as there are at least two hundred and 



