INSECTS: STINGS AND OVIPOSITORS 155 



same way as a carpenter's hand- saw, supposing the tendons 

 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 simi- 

 lar, 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 unknown to 

 our mechanics; for two or three are sometimes fixed in 

 the same frame. These, however, not only all move up- 

 ward and downward simultaneously, but cut the wood 

 in different places; while the two saws of the ovipositor 

 work in the same cut, and, consequently, though the teeth 

 are extremely fine, the effect is similar to [that of] 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 operation 

 and this, also, nature has provided for by lodging the 

 backs of the saws in a groove, formed by two membranous 

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

 plates are thickest at the base, becoming gradually thinner 

 as they approach the point which the form of the saws re- 

 quires. According to Valisnieri, it is not the only use of 

 this apparatus to form a back for the saws, he having dis- 

 covered between the component membranes two canals, 

 which he supposes are employed to conduct the eggs of 

 the insect into the grooves which she 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 with fine teeth. The latter, also, 

 combines at the same time the properties of a saw and of 



