AFFECTION OP INSECTS FOR THEIR YOUNG. 555 



rural walk will open to you, while witnessing in the ani- 

 mals themselves those marks of affection for their un- 

 seen progeny of which I have endeavoured to give you 

 a slight sketch, it will be none of the least fertile to 

 examine the various and appropriate instruments with 

 which insects have been furnished for the effective exe- 

 cution of their labours. The young of the saw-fly tribe 

 {Serrifera^) are destined to feed upon the leaves of rose- 

 trees and various other plants. Upon the branches of 

 these the parent fly deposits her eggs in cells symme- 

 trically arranged ; and the instrument with which she 

 forms them is a saw, somewhat like ours but far more in- 

 genious and perfect, being toothed on each side, or rather 

 consisting of two distinct saws, with their backs (the teeth 

 or serratures of which are themselves often serrated, and 

 the exterior flat sides scored and toothed), which play 

 alternately ; and, while their vertical effect is that of a 

 saw, act laterally as a rasp. When by this alternate 

 motion the incision, or cell, is made, the two saws, re- 

 ceding from each other, conduct the egg between them 

 into it''. The Cicada, so celebrated by the poets of an- 

 tiquity, which lays its eggs in dry wood, requires a 

 stronger instrument of a different construction. Ac- 

 cordingly it is provided with an excellent double auger, 

 the sides of which play alternately and parallel to each 

 other, and bore a hole of the requisite depth in very hard 

 substances without ever being displaced. 



The construction of the sting or ovipositor with which 



* Latreille denominates this tribe Secnrifera; but as the tool of 

 these insects resembles a saw and not a hntchet, we have ventured to 

 change it to Serrifera, which is more appropriate. 



'' Prof. Peck's Nat. Hist. oftheSlug-ivorm, t.\2.f. 12-14. Plate XV. 

 Fig. 21. 



2 A 2 



