102 Obfcrvations on the HeJJian Fly. 



It may not be improper here to mention fome few experi- 

 ments and obfcrvations which I have made on this fubjeft; 

 all of which appear to confirm the foregoing opinion refpefting 

 the number of generations which this infeQ paffes through in a 

 year. A number of the chryfahs gathered from the wheat, about 

 the middle of laft June, were kept in the houfe in glaffes, and 

 in actuation where they were not expofed to the rays of the 

 fun, and a part of thofe were transformed into a fly between 

 the lOth and the 1 3th of September ; and a number of others 

 gathered from the ftubble after harveft, and placed in the fame 

 fituation, became a fly about the fame time. The remainder 

 of thofe, which were not transformed into a fly at that time^ 

 continued in the fame flate until the weather became too cold 

 for them to make their transformation. In the year eighty- 

 feven, I made experiments of a fmiilar nature, with only this 

 difference, that the chrylalis was expofed to the rays of the fun 

 in fuch manner that the heat would not be too violent, and in 

 this cafe, a few of them were transformed into a fly, as early as 

 the middle of Augult. It mull however be obferved, that in 

 all experiments made in this manner, there is reafon to fuppofe 

 fome degree of uncertainty, becaufe the chryfilis is removed 

 from its natural fltuation : for this reafon I have always 

 fuppofed, that the befl; method to arrive at truth on this fubjed, 

 is to examine the progrefs of the infeO; in the field ; and with 

 diis view I examined the fl:ubble of a field of wheat, where 

 great numbers of the infe6l were to be found, as often as 



