INSECTS. 501 



into the fissure made by the saws in the leaf. The 

 cutting edges of the saws are provided with about eighteen 

 or twenty teeth, these have sharp points of extreme 

 delicacy, and together making a serrated edge of the exact 

 form given to the finest and best-made surgical saws. In 

 the summer-time the proceedings of this little insect can 

 be watched, and the method of using this curious instru- 

 ment seen, by the aid of a hand magnifying-glass ; they 

 are not easily alarmed when busy at their work. 



Many other insects are provided with instruments for 

 boring into the bark or solid wood itself. The Cynvp bores 

 a hole into the side of the oak-apple, 

 for the purpose of depositing its egg, 

 the larva when hatched finds a com- 

 fortable lodging, and a good supply 

 of food; when full grown, it eats its 

 way out of the nut, and dropping to 

 the ground, it assumes the form of 

 the perfect fly. The most important 

 of this family is the Cynip galloe tino- 



torice, fig. 257, Which is the Cause Of Fig. 257. FemaleEglan- 



the gall-nut, a nut most extensively em- tine Gall ~^ <* ndLar ' 

 ployed in the manufacture of ink and for dyeing purposes. 

 Some of the Wasp tribe, so very peculiar in their habits, 

 are active agents in the economy of nature. The Solitary, 

 Mason-wasps, curiously construct nests in the form of 

 cells, for the purpose of carefully rearing their young. 

 The social wasps, like bees, live in communities, and 

 have nearly the same divisions of labour and regulations 

 for the good government of their colony. The struc- 

 ture and mechanical contrivance of the wasp's sting can 

 only be seen under the microscope. The sting consists of 

 two barbed darts, which will penetrate the flesh deeply, 

 and from a peculiar arrangement of their serrated edges, 

 their immediate withdrawal is prevented; by the great 

 muscular effort required for this purpose, a small sac or 

 bag near the root is pressed upon, and its irritating con- 

 tents squeezed out into the wound. After the fluid is 

 injected, the wasp has the power of contracting the 

 barbed points, and then it withdraws the sting from its 

 victim. In fig. 258 the sting of the wasp is shown, with 



