INSECTS. HYMENOPTERA. 



311 



purpose of cutting the leaf, is one of the most remarkable pieces of per- 

 fect mechanism : it is securely lodged, when not in use, in a long nar- 

 row slit beneath the hinder part of the abdomen, bounded by two horny 



fig. 141. The Saw-fly of the Gooseberry. 



plates. At first these appear to consist of a single piece ; but upon 

 closer inspection four plates are found to enter into their construction : 

 namely, two saws, placed side by side, as in fig. 142 ; and two supports, 

 very like the saws in shape. A deep groove runs along the thick edge 



fig. 142. Saws of Saw-fly, 



In the small circle is represented the comparative size of these instruments ; they are 

 drawn rather too small. 



of the latter, which is so arranged that the saws run backwards or for- 

 wards, without the possibility of getting out of the groove. When the 

 cut is made, the four are drawn together ; and through the central 

 canal, which is now formed by combining the whole, an egg is pro- 

 truded into the fissure made by the saws in the leaf. The cutting 

 edges of the saws are provided with about eighteen or twenty teeth, 



