160 INTERNAL ANATOMY OF INSECTS. 



sheath, two augers or borers, and an intermediate piece 

 upon which they slide, each being furnished with an 

 internal groove for that purpose, and the middle piece 

 with a ridge to fit; a contrivance of Divine Wisdom, 

 to prevent their dislocation when employed in boring ; 

 the augers terminate in a knob which is externally 

 toothed a . This structure approaches that of the Hi/- 

 menoptera, especially the saw-flies. With regard to 

 the Heteropterous section of this Order as they usually 

 do not introduce their eggs into any substance, they have 

 no call for any remarkable ovipositor, and therefore are 

 not so furnished. A remark which will also apply to 

 the Lepidoptera Order. 



In the Libellulina amongst the- Neuroptera, an organ 

 of this kind is sometimes discoverable. In Agrion, Reau- 

 mur noticed a part which he conjectured to be an ovi- 

 positor ; it consists of four lamina or lancets, the interior 

 pair slender, the exterior wider, and all externally ser- 

 rated b . 



The insects of the Hymenoptcra Order have long been 

 celebrated for the organs we are describing, whether 

 used as saws, augers, or darts. I formerly gave you a 

 very general account of the saws, I shall now give you 

 a very interesting one in detail copied from an admi- 

 rable little essay of Professor Peck. " This instru- 

 ment," says he, " is a very curious object ; and 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 pre- 

 vent its bending. The back is a piece of iron, in which 

 a narrow and deep groove is cut to receive the plate, 



a Reauiti. v. 177. b Md. vi. 435. t. xl./. 6, 7. 



