132 EVENINGS AT THE MICROSCOPE. 



themselves denticulated with fine 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 instrument, resembling in their form 

 and setting the teeth of a comb. " * 



Now 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 portion 

 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 double-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 discrepancy in the 

 detail, and many points not noticed ; — in part, doubtless, 

 owing to its being another species which was under 

 observation, and partly to the inferiority of the micro- 

 scopes employed a hundred and fifty years ago to those 

 we are using. 



In the first place, the curve of the f is different, the 

 convexity of the edge being towards the point and the 

 concavity nearest the base. Then the strengthening does 

 not appear to me a groove in which the saw plays, but 

 a thickening of the substance of the back. Each main 

 tooth of the saw in this case is the central point in the 

 edge of a square plate, which appears to be slightly con- 

 cave on its two surfaces, being thickened at its two sides, 

 at each of which, where it is united to the following plate, 

 it rises, and forms with it a prominent ridge running trans- 



* "Insect Architecture," 153. 



