4 NATURAL HISTORY 



Caterpillars are exceedingly numerous and gener- 

 ally known ; there are however other larvae, which bear a 

 confiderable refemblance to them; but are transformed 

 to infects widely different : Naturalifts have called them 

 falfe caterpillars. The largeft of thefe that I have feen, 

 were upon the White Birch and the Willow. Thofe 

 which inhabit the willow are common enough : They 

 are fmooth and black, with a feries of yellow fpots ori 

 each fide, along the whole length of the body. They feed 

 in ranks arranged along the edges of the leaves, and throw 

 themfelves into very odd attitudes. Examined with a 

 magnifier, they are found to have the fix firft feet, armed 

 with a fingle claw, like the caterpillar ; but the other 

 feet are more numerous, and rnftead of being furnifhed 

 with a number of little hooks, as in the caterpillar, are 

 only retractile prominences terminated by a foft, fmooth, 

 and rounded furface. 



I give you this defcription, Sir, and refer you, for the 

 obfervation of the federal particulars of it, to the black 

 larva v/hich infefts the willow, as it is large enough to be 

 eafily examined, becaufe the Slug, which feems at prefent 

 to threaten the deftruction of fome of our beft fruit-trees, 

 is of the fame family. 



It is faid to be about eight or ten years, fince the Slug 

 was firft obferved in gardens, in the county ofEffex, from 

 whence it is fuppofedto have fpread. 



Having been in the habit of frequently vifiting mj 

 trees, in order to deflroy the canker and web-worms, or 

 other infects which infefted them, I think I fhould have 

 feen the Slug if it had been in my garden; but it was not 

 till the 8th. of July, 1796, that I faw any on my trees 1 

 I will not however affert, that it did not inhabit them be- 

 fore, infuch fmall numbers as to elude obfervation. 



On the 12th of July I plucked fome leaves on which 

 the Slugs were feeding ; and having filled a glafs veflel 

 with light earth, laid the leaves upon it ; by the 19th thefe 

 bad all ceafed to feed, and having thrown off the (limy 

 (kin, appeared in a yellow one, and defcended into the 

 earth. A few which had entered the earth at the fidei 



of' 



