162 INSECTS. 



If so charming a writer as Mr. Kirby (Spence ?) could 

 do no better than borrow a description of this wonderful 

 little tool, it is hoped that a humbler writer may well be 

 forgiven for following in his steps, and for presenting to 

 the reader the account of Professor Peek, quoted in the 

 "Introduction to Entomology :" "This instrument is 

 a very curious object ; in order to describe it, it will be 

 proper to compare it with the tenon saw used by cabinet 

 makers, which being made of a very thin plate of steel, 

 is fitted with a back to prevent its bending. The back 

 is a piece of iron, iu which a narrow and deep groove is 

 cut to receive the plate, which is fixed. The saw of the 

 Tenthredo is also furnished with a back, but the groove 

 is in the plate, and receives a prominent ridge of the 

 back which is not fixed, but permits the saw to slide for- 

 ward or backward as it is thrown out or retracted. The 

 saw of artificers is single, but that of the Tenthredo is 

 double, and consists of two distinct saws with their backs. 

 The insect, in using them, first throws out one, and 

 while it is returning pushes forward the other; and this 

 alternate motion is continued till the incision is effected, 

 when the two saws, receding from each other, conduct 

 the egg between them into its place. In the artificial 

 saw the teeth are alternately bent towards the sides, or 

 out of the right line, in order that the fissure or skerf 

 may be made sufficiently wide for the blade to move 

 easily. To answer this purpose in some measure, in that 

 of the Tenthredo the teeth are a little twisted, so as to 

 stand obliquely with respect to the right line, and their 

 point of course projects a little beyond the place of the 

 blade without being laterally bent, and all those in each 

 blade thus project a little outwards. But the skerf is 

 more effectually made and a free range procured for the 



