SAW-FLIES. 133 



splinters of the wood, detached at one end, but left fixed 

 at the other by the insect. These elevations are for the 

 most part in a line, rarely in a double line, nearly at 

 equal distances from each other, and form a lid to a 

 cavity in the wood about four lines in length, containing 

 from four to ten eggs. It is to be remarked, that the 

 insect always selects a branch of such dimensions, that it 

 can get at the pith, not because the pith is more easily 

 bored, for it does not penetrate into it at all, but to form 

 a warm and safe bed for the eggs. M. Pontedera says, 

 that when the eggs have been deposited, the insect closes 

 the mouth of the hole with a gum capable of protecting 

 them from the weather ; but M. Eeaumur thinks this only 

 a fancy, as, out of a great number which he examined, he 

 could discover nothing of the kind. Neither is such a pro- 

 tection wanted ; for the woody splinters above mentioned 

 furnish a very good covering. 



The grubs hatched from these eggs (of which, M. Pon- 

 tedera says, one female will deposit from five to seven 

 hundred) issue from the same holes through which the 

 eggs have been introduced, and betake themselves to the 

 ground to feed on the roots of plants. They are not 

 transformed into chrysalides, but into active nymphs, 

 remarkable for their fore limbs, which are thick, strong, 

 and furnished with prongs for digging ; and when we are 

 told, by Dr. Le Fevre, that they make their way easily 

 into hard stiff clay, to the depth of two or three feet, we 

 perceive how necessary to them such a conformation 

 must be. 



Saw-Flies . 



An instrument for cutting grooves in wood, still more 

 ingeniously contrived than that of the tree-hopper, was 

 first observed by Vallisnieri, an eminent Italian naturalist, 

 in a four-winged fly, most appropriately denominated by 

 M. Eeaumur the saytyfly (Tenthredo), of which many sorts 

 are indigenous to Great Britain. The grubs from which 

 those flies originate are indeed but too well known, as the}' 

 frequently strip our rose, gooseberry, raspberry, and red 



