INSECTS : STIXGS AND OVIPOSITORS. 151 



a clasp-knife. These plates are thickest at tlie base, 

 becoming gradually thinner as they approach tlie 

 point which the form of the saws requires. According 

 to Yalisnieri, it is not the only use of this apparatus 

 to form a back for the saws, he having discovered be- 

 tween the component membranes two canals, which he 

 eupposes are employed to conduct the eggs of the in- 

 sect into the grooves which she has hollowed out for 

 them. 



" Tlie teeth of a carpenter's saw, it may be re- 

 marked, are simple, whereas the teeth of the ovipositor- 

 saw are themselves denticulated with jSne teeth. The 

 latter, also, combines at the same time the properties 

 of a saw and of a rasp or file. So far as we are aware, 

 these two properties have never been combined in any 

 of the tools of our carpenters. The rasping part of 

 the ovipositor, however, is not constructed like our 

 rasps, with short teeth thickly studded together, but 

 has teeth almost as long as those of the saw, and 

 placed contiguous to them on the back of the instru- 

 ment, resembling in their form and setting the teeth of 

 a comb." * 



K^ow look at this object which I have just extracted 

 from the abdomen of a rather large female Saw-fly, of 

 a bright green hue, spotted with black. The first por- 

 tion of the apparatus that protruded on pressure, was 

 this pair of saws of an y*-like figure. These agree in 

 general with those described ; here is, in each, the 

 doubly-curved blade, the strengthened back, the rasp- 

 like jagging of the lateral surfaces, the teeth along the 

 edge, and the secondary toothlets of the latter. All 

 these essential elements we see, but there is much dis* 



* Insect Architecture, 153. 



