166 Insect Architecture. 



very small ones, beside the nine that are more obvious. The 

 magnifier also shows that the instrument itself, which appeared 

 simple to the naked eye, is, in fact, composed of three differ- 

 ent pieces ; two exterior armed with the teeth before men- 

 tioned, denominated by Keaumur files (limes), and another 

 pointed like a lancet, and not denticulated. The denticulated 

 pieces, moreover, are capable of being moved forwards and 

 backwards, while the centre one remains stationary ; and as 

 this motion is effected by pressing a pin or the blade of a 

 knife over the muscles on either side at the 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 

 extent. 



The contrivance by which those three pieces are held 

 united, while at the same time the two files can be easily put 

 in motion, is similar to those of our own mechanical inven- 

 tions, with this difference, that no human workman could 

 construct an instrument of this description so small, fine, 

 exquisitely polished, and fitting so exactly. We should have 

 been apt to form the grooves in the central piece, whereas 

 they are scooped out in the handles of the files, and play 

 upon two projecting ridges in the central piece, by which 

 means this is rendered stronger. M. Eeaumur discovered 

 that the best manner of showing the play of this extraor- 

 dinary 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, as is shown in 

 the lower figure. 



M. Pontedera, who studied the economy of the tree-hoppers 



