232 THE XYLOPHAGA. 



beyond the apex of the abdomen in the form of a 

 stout^ pointed tail. The apex of the abdomen also is 

 produced into a tail in the females. In their general 

 form they closely resemble the Saw-flies^ from which^ 

 however, the males, as well as the females, may be 

 distinguished by the distinct neck which separates 

 the head from the thorax, and the possession of only 

 a single spur at the apex of the anterior tibiae, the 

 members of the preceding tribe exhibiting a pair of 

 those organs. 



The object of the complete change in the con- 

 struction of the OAdpositor in these insects, which, 

 like the Saw-flies, feed upon vegetable matter in the 

 larva state, is at once apparent when we become 

 acquainted with the particulars of their mode of life. 

 Their larvse, instead of feeding, like those of the Phyllo- 

 phaga, upon the tender parenchyma of the leaves of 

 plants, devour the hard woody portions of their stems, 

 and consequently, instead of forming a mere slit for 

 the reception and protection of the eggs, the perfect 

 insect has to introduce her offspring into the wood of 

 trees, a purpose for which the saws of the Tenthredos, 

 beautiful as they are in their structure, would be 

 totally inadequate. The larva produced from the 

 egg thus deposited is a cylmdrical fleshy grub, fur- 

 nished with a small horny head, and six minute 

 legs. The mouth is armed with a pair of strong 

 mandibles of remarkable structure, which the insect 

 uses most effectively in eating its way through the 

 timber. When full-grown, the larv?e bmTow deeper 

 into the trunk of the tree, often to a depth of several 

 inches, where they form a chamber in which to pass 

 through their pupa state ; and as the insects often 

 occur in great numbers, and some of them are of 



