SAW-FLIES. 153 



some of the most common have a flat body of a 

 yellow or orange colour, while the head and shoulders 

 are black. 



In order to see the ovipositor to which we shall 

 for the present turn our chief attention, a female saw- 

 fly must be taken, and her belly gently pressed, when 

 a narrow slit will be observed to open at some dis- 

 tance from the anus, and a short, pointed, and some- 

 what curved body, of a brown colour and horny sub- 

 stance, will be protruded. The curved plates which 

 tbrm the sides of the slit, are the termination of the 

 sheath, in which the instrument lies concealed till it 

 is wanted by the insect. The appearance of this in- 

 strument, however, and its singular structure, cannot 

 be well understood without the aid of a microscope. 



a. Ovipositor oj' Saw-fly, protruded from its Sheath, magniefid. 



The instrument thus brought into view, is a very 

 finely contrived saw, made of horn, and adapted 

 for penetrating branches and other parts of plants 

 where the eggs are to be deposited. The ovipo- 

 sitor saw of the insect is much more complicated 

 than any of those employed by our carpenters. The 

 teeth of our saws are formed in a line, but in such 

 a manner as to cut in two lines parallel to, and at 

 a small distance from each other. This is effected 

 by slightly bending the points of the alternative teeth 

 right and left, so that one half of the whole teeth 



