156 EVENINGS AT THE MICROSCOPE 



a rasp or file. So far as we are aware, these two proper- 

 ties 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 /-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 tooth- 

 lets 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 in- 

 feriority of the microscopes employed a hundred and fifty 

 years ago to those we are using. 



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

 convexity of the edge being toward 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 

 square plate, which appears to be slightly concave on its 

 two surfaces, being thickened at its two sides, at each of 



1 "Insect Architecture," 153. 



