246 NATURAL HISTORY. [CH. XVII. 



CHAPTER XVII. 



THE NATURAL HISTORY OF VARIOUS SPECIES OF SAWFLIES. 



An account of the Ovipositor, and Sawing Apparatus — An accoiint 

 of the Rose Sawfly — Description of their Eggs, LarvcB, 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, v/e 

 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-d-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 



