136 INSECT ARCHITECTURE. 



attached to its base to form the handle, and the muscles 

 which put it in motion to be the hand of the carpenter. 

 But the carpenter can only work one saw at a time, 

 whereas each of these flies is furnished with two, equal 

 and similar, which it works at the same time — one being 

 advanced and the other retracted alternately. The secret, 

 indeed, of working more saws than one at once is not un- 

 known to our mechanics ; for two or three are sometimes 

 fixed in the same frame. These, however, not only all 

 move upwards and downwards simultaneously, but cut the 

 wood in different places ; while the two saws of the ovi- 

 positor work in the same cut, and consequently, though 

 the teeth are extremely fine, the effect is similar to a saw 

 with a wide set. 



It is important, seeing that the ovipositor-saws are so 

 fine, that they be not bent or separated while in opera- 

 tion — and this, also, nature has provided for, by lodging 

 the backs of the saws in a groove, formed by two mem- 

 braneous plates, similar to the structure of a clasp-knife. 

 These plates are thickest at the base, becomiijg gradually 

 thinner as they approach the point which the form of the 

 saws requires. According to Vallisnieri, it is not the 

 only use of this apparatus to form a back for the saws, he 

 having discovered, between the component membranes, 

 two canals, which he supposes are employed to conduct the 

 eggs of the insect into the grooves which it has hollowed 

 out for them.* 



The teeth of a carpenter's saw, it may be remarked, 

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

 themselves denticulated Avith 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 pro23er- 

 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 

 '* Eeaumiu-, Mem. des Insectes, v. p. 3. 



