15-2 INSECT ARCHITECTURE. 



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 men- 

 tioned furnish a very good covering. 



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

 Ponledera 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 appro- 

 priately denominated by M. Reaumur the saw-Jly 

 (Tcnthredd), of which many sorts are indigenous to 

 Great Britain. The grubs from which those flies 

 originate are indeed but too well known, as they fre- 

 quently strip our rose, gooseberry, raspberry, and red 

 currant trees of their leaves, and are no less destruc- 

 tive to birch, alder, and willows ; while turnips and 

 wheat suffer still more seriously by their ravages. 

 These grubs may readily be distinguished from the 

 caterpillars of moths and butterflies, by having from 

 sixteen to twenty-eight feet, by which they usually 

 hang to the leaf they feed on, while they coil up the 

 hinder part of their body in a spiral ring. The perfect 

 flies are distinguished by four transparent wings; and 



