284 NOTES ON NATURAL HISTORY BOOKS. 



beautifully constructed saw (hence the common name), for the pur- 

 pose of depositing its eggs therein. The mother Saw Fly, having 

 selected a branch adapted to her object, alights upon it, and com- 

 mences to cut a groove in it with her saw, which is situated near 

 the anal extremity of her body, and is well fitted for its office, being 

 furnished with two rows of teeth capable of separate and continued 

 action, so that when one row of teeth is protruded iorwards, the 

 other is drawn backwards, thus giving the insect all the advantage 

 of two saws. This instrument is not only a saw, but is also a rasp ; 

 for each of its teeth, upon examination, is found to be furnished 

 with several sharp and parallel ridges : in which respect it ] assesses 

 a superiority over the saws used by our mechanics. Many inven- 

 tions in daily use among us, we know, were originally suggested by 

 the structure of animals ;* but it strikes me as somewhat strange 

 that no one has hitherto made a saw upon this principle. We fur- 

 ther find that this instrument is not merely a saw and a rasp, 

 but is likewise an ovipositor, having a hollow channel passing 

 through it from the base to the apex. When the groove in the 

 branch is ready for the reception of the egg, the saw ceases its ope- 

 ration, and next performs its extra duty of ovipositor by depositing^ 

 in proper order, the eggs as they issue from the oviduct. So soon 

 as an egg is laid, the ovipositor is retracted a little, but speedily 

 again protruded ; and a small quantity of liquid matter, of a frothy 

 appearance, is then observed to fall upon the egg, and is probably 

 intended to gum it to its bed. After the eggs are deposited in the 

 groove, the cut in the branch is not conspicuous at first, but it at 

 length assumes a blackish colour, and becomes raised. ' This in- 

 creased elevation' is said, by the author of Insect Architecture, who 

 appears formerly to have devoted considerable time and attention to 

 the study of insects, not to be * owing to the growth of the bark, 

 the fibres of which, indeed, have been destroyed by the ovipositor 

 saw, but to the actual growth of the egg ; for when a new-laid egg 

 of the Saw F]y is compared with one which has been several days 

 enclosed in the groove, the latter will be found to be very consider- 

 ably the larger.' He also states that, as the egg ' continues to 

 increase, it raises the bark more and more, and consequently widens, 



* We think some philosophers are much too fond of determining the ha- 

 bitudes and inventions of man, to be derived from the lower animals ; as if 

 the lords of the creation were not in possession of innate faculties to render 

 him competent to achieve anything original ! Some have actually gone so 

 far as to state that the idea of vocal and other music had its origin in the 

 singing of birds ! — Eds. 



