THE SAW-FLIES. 227 



ought to receive these in its embrace ; and, according 

 to Burmeister, the only trace of this is a small tubercle 

 which exists at the base of the serrated plates, which 

 it serves to keep asunder at this point, whilst Mr. 

 Westwood, on the contrary, considers that this part 

 of the organ is completely split instead of being chan- 

 neled, and that its two halves are amalgamated with 

 the serrated bristles, of which they would then form 

 the dorsal portion. 



Be this as it may, the use of the organ at any rate 

 is no mystery. The insects, which have received the 

 common English name of Saw-flies from their posses- 

 sion of this very appendage, visit the plants, which 

 they are told by some unerring instinct will affbrd 

 the proper description of food for their off'spring, and 

 there, selecting a suitable position, cut little slits in 

 the bark or leaves by means of the two serrated 

 plates, which work alternately, and appear to com- 

 bine the action of the saw and rasp. In each of 

 these slits the female Saw-fly deposits an egg, accom- 

 panied by a drop of viscid froth, which is supposed 

 by some authors to prevent the wound from closing 

 over the egg, and may probably also have some influ- 

 ence upon the preservation of the latter. Before 

 hatching, the eggs increase to double their original 

 size, probably from the imbibition of the moisture 

 which surrounds them, and the little saw- cut in 

 which they are deposited also expands in the same 

 proportion. 



The larvae of the majority of the insects of this 

 tribe resemble the gooseberry- grub above referred to, 

 and the well-known caterpillars of the ordinary butter- 

 flies and moths in their general appearance; they are 

 soft and fleshy, with a horny head, and six jointed 



