HYMENOPTERA. 415 



and the slimy grub of the pear-tree in Europe. So different 

 are these from the other false caterpillars, that tiiey would not 

 be suspected to belong to the same family. Their relationship 

 becomes evident, however, when they have finished their trans- 

 formations ; and accordingly we find that the saw-flies of our 

 slug- worms and those of the vine are so much alike in form 

 and structure, that they are both included in the same f^-enus. 

 Moreover, there are certain false caterpillars intermediate in 

 their forms and appearance between the slimy and slug-like 

 kinds and those that more nearly resemble the true caterpiUars; 

 thus admirably illustrating the truth of the remark, that nature 

 proceeds not with abrupt or unequal steps ; * or, in other words, 

 that amidst the immense variety of living forms, wherewith 

 this earth has been peopled, there is a regular gradation and 

 connexion, wliich, in particular cases, if we fail to discover, it 

 is rather to be attributed to our own ignorance and short- 

 sightedness than to any want of harmony and regularity in 

 the plan of the Creator. In considering the resemblances of 

 species, we cannot fail to admire the care that has been 

 taken, by almost insensible shades of difference among them, 

 or by peculiar ckcumstances controlling their distribution, 

 their habits of life, and their choice of food, to prevent them 

 from commingling, whereby each species is made to preserve 

 forever its individual identity. 



The saw-fly of the rose, which, as it does not seem to have 

 been described before, may be called Selandria Ros(e, from its 

 favorite plant, so nearly resembles the slug-worm saw-fly as 

 not to be distinguished therefrom except by a practised ob- 

 server. It is also very much like Selandria barda, Vitis, and 

 pyg-mcEa, but has not the red thorax of these three closely allied 

 species. It is of a deep and shining black color. The first 

 two pairs of legs are brownish gray or dirty white, except the 

 thighs, which are almost entkely black. The hind legs are 

 black, with whitish knees. The wings are smoky, and trans- 

 parent, with dark brown veins, and a brown spot near the 

 middle of the edge of the first pair. The body of the male is 



* Natura saltus nou facit. Linnaeus. Syst. Nat. I. 11. 



