Tree-Hoppers. 169 



willows ; while turnips and wheat suffer still more seriously 

 by their ravages. These grubs may readily be distinguished 

 from the caterpillars of moths and butterflies by having from 

 sixteen to twenty-eight feet, by which they usually hang to 

 the leaf they feed on, while they coil up the hinder part of 

 their body in a spiral ring. The perfect flies are distin- 

 guished by four transparent wings ; and 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 distance from the apex, and a 

 short, pointed, and somewhat curved body, of a brown colour 



a, Ovipositor of Saw-fly, protruded from its slieath, magnified. 



and horny substance, will be protruded. The curved plates 

 which form 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 instrument, 

 however, and its singular structure, cannot be well under- 

 stood without the aid of a microscope. 



The instrument thus brought into view is a very finely- 

 contrived saw, made of a horny substance, and adapted for 

 penetrating branches and other parts of plants where the 

 eggs are to be deposited. The ovipositor-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 



