mSKCTS : STINGS AND OVIPOSITORS. 149 



coutemporaiy Valisnieri. Their details I shall first cite, 

 as they have been put into an English dress by Rennie, 

 and then show you a specimen dissected out by myself, 

 and point out some agreements and some discreiiancies 

 between it and them. 



" In order to see the ovipositor, a female saw-fly 

 must be taken, and her belly gently pressed, when a 

 narrow slit will be observed to open at some distance 

 from the anus, and a short, pointed, and somewhat 

 curved body, of a brown colour and horny substance, 

 will be protruded. The curved plates which form the 

 sides of the slit, are the termination of the sheath, in 

 which the instrument lies concealed till it is wanted by 

 the insect. 



" The instrument thus brought into view, is a very 

 finely contrived saw, made of horn, and adapted for 

 penetrating branches and other parts of plants where 

 the eggs are to be deposited. The ovipositor-saw of 

 the insect is much more complicated than any of those 

 employed by our carpenters. The teeth of our saws 

 are formed in a line, but in such a manner as to cut in 

 two lines parallel to and at a small distance from each 

 other. This is effected by slightly bending the points 

 of the alternate teeth right and left, so that one half of 

 the whole teeth stand a little to the right, and the other 

 half a little to the left. The distance of the two parallel 

 lines thus formed is called the course of the saw, and it 

 is only the portion of wood which lies in the course 

 that is cut into sawdust by the action of the instru- 

 ment. It will follow, that in proportion to the thin- 

 ness of a saw there will be the less destruction of wood 

 which may be sawed. When cabinet-makers have to 

 divide valuable wood into very thin leaves, they ac- 



