524 HYMENOPTERA. 



in number, and in the year 1832 they had become so 

 numerous and destructive that many vines were entirely 

 stripped of their leaves by them. Whether the remedies 

 then proposed by me, or any other means, have tended to 

 diminish their numbers, or to keep them in check, I have 

 not been able to ascertain, and have had no further oppor- 

 tunity for making observations on the insects themselves. 

 At that time, air-slacked lime, which was found to be fatal 

 to these false caterpillars of the vine, was advised to be 

 dusted upon them, and strewed also upon the ground un- 

 der the vines, to insure the destruction of such of the in- 

 sects as might fall. A solution of one pound of common 

 hard soap in five or six gallons of soft water is used by 

 English gardeners to destroy the young of the gooseberry 

 saw-fly ; and the same was recommended to be tried upon 

 the insects under consideration. 



All the young of the saw-flies do not so closely resemble 

 caterpillars as the preceding ; some of them, as has already 

 been stated, have the form of slugs or naked snails. Of 

 this description is the kind called the slug- worm in this 

 country, and the slimy grub of the pear-tree in Europe. 

 So different are these from the other false caterpillars, that 

 they would not be suspected to belong to the same family. 

 Their relationship becomes evident, however, when they 

 have finished their transformations : and according" we 



9 O v 



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 genus. 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 caterpillars ; thus admi- 

 rably illustrating the truth of the remark, that nature pro- 

 ceeds 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 



* " Xatura saltus non facit." Linnaeus, Syst. Xat. I. 11. 



