158 ETENmes at the microscope. 



origin of the ovipositor, it may be presumed that those 

 muscles are destined for producing similar movements 

 when the insect requires them. By means of a finely- 

 pointed pin carefully introduced between the pieces, 

 and pushed very gently downwards, they may be, 

 with no great difficulty, separated in their whole ex- 

 tent. 



" The contrivances by which those three pieces are 

 held imited, while at the same time the two files can be 

 easily put in motion, are similar to some of our own 

 mechanical inventions, with this difference, that no hu- 

 man workman could construct an instrument of this 

 description so small, fine, exquisitely polished, and fit- 

 ting so exactly. We should have been apt to form the 

 grooves ia the central piece, whereas they are scooped 

 out in the handles of the files, and play upon two pro- 

 jecting ridges in the central piece, by which means this 

 is rendered stronger. M. Keaumur discovered that the 

 best manner of showing the play of this extraordinary 

 instrument is to cut it off with a pair of scissors near its 

 origin, and then, taking it between the thumb and the 

 finger at the point of section, work it gently to put the 

 files in motion. 



" Beside the muscles necessary for the movement of 

 the files, the handle of each is terminated by a curve 

 of the same hard horny substance as itself, which not 

 only furnishes the muscles with a sort of lever, but 

 serves to press, as with a spring, the two files close to 

 the central piece." * 



The use of these instruments is the same as I have 

 already alluded to in the ease of the saw-fiies. The 

 female Tree-hopper deposits her eggs in holes which she 



* Insect Architecture, 149. 



