§ NATURAL HISTORY 



enter the earth to the depth of frpm one to four inches* 

 and the procefs of transformation goes on as related a- 

 bove. 



Frequently as foon as the fkin is fhed, they are ^en 

 feeding upon it; this appears to be an inftin&ive aft, and 

 perhaps contributes to fumifh a more copious fupply of 

 the vifcous exudation; but the laft mucous fkin which is 

 thrown off remains extended on the leaf, as at j£g*. 2. c, 

 and fuch (kins have been miftaken for dead (lugs. 



On the 12th of July, perceiving many in the yellow 

 fkin, I directed cloths to be fpread on the ground and 

 the trees to be fhaken: About 170 were collected which 

 I threw into a veffel filled with light earth. On the 30th, 

 or in eighteen days after their defcent into the earth they 

 began to rife in the form of flies. 



I was then unexpectedly called from home, and was 

 abfent through the months of Auguft and September. 

 At my return, in O&ober, the flugs of the fecond hatch 

 were in plenty on the trees, and fome of them remained 

 till the 21ft, a month later thaji in the preceding year, 

 when almoft all the leaves had fallen and after having 

 furvived feveral frofts. 



They had been far more numerous in the firft hatch, 

 than they were in 1796; but according to the beft infor- 

 mation I could colled, their numbers in the fecond great- 

 ly exceeded the firft : the fmall trees were covered with 

 them ; and a breeze of air pafling through the trees, 

 became charged with a very difagreeable and almoft fick- 

 ening odour. 



In order to determine, with fome degree of precifion, 

 the time when the fly firft rifes in the fpring, I filled a 

 box with earth taken from the foot of a cherry tree, from 

 one to four inches deep, in the month of February of 

 the prefent year. It contained about two cubic feet. 

 This earth I caufed to be fined, and by this means 199 

 cells were collected, which were put with fome of the 

 fifted earth in a garden pot. At the fame time I exam- 

 ined the earth in which the larvae of the firft hatch 

 of the laft year had paffed their transformation ; and 



finding 



