HYMENOPTERA. 379 



vious to the publication of my "Discourse," I observed that 

 these insects annually increased 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 under the vines, to insure the 

 destruction of such of the insects 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 cat- 

 erpillars as the preceding ; some of them, as has already been 

 stated, have the form of slugs or naked snails. Of this descrip- 

 tion 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 evi- 

 dent, however, when they have finished their transformations ; 

 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 genus. Moreover, there are 

 certain false caterpillars intermediate in their forms and appear- 

 ance between the slimy and slug-like kinds and those that more 

 nearly resemble the true caterpillars ; 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, which, 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 



* Naturasaltus non facit. Linnaeus. Syst. Nat. I. 11. 



