Ohfervations on the Hejjian Fly. 103 



twice in a week, from the ruft of September until tlie 1 4th of 

 N^ovember in the lafl fall, and found them continually to diminifli 

 in number, but that there were ftill fome few of the chry falls re- 

 maining. Thefe I have fuppofed muft either be confidered as fome 

 few which were anomalous, and never intended by nature to 

 undergo any transformation ; or elfe it mufl be concluded, that 

 many of thofe which become a chiyfalis late in the month of 

 June, will remain in that ftate f^r fo long a time, that the weather 

 will become too cold for them to be transformed into a fly in 

 the fall, and then they mud necelTarily continue in that ftate 

 through the Vv inter, until it becomes warm enough in the fpring: 

 and if this latter conclufion be confident with truth, it will 

 follow, that fo far as refpefts thefe, there can be only one 

 generation in a year. It is an opinion entertained ;by many, 

 that there are three generations of this infe6l in a year; but in 

 anfwer to this, I fhall only obfervc, that independent of what 

 has been before faid on this fubj eel, this opinion mud appear 

 improbable from this con fide ration — that if we fuppofe three 

 generations in a year, it will follow, that the infed will be twice 

 a fly before harveft, and the fecond time of its being a fly muft 

 happen when the wheat is in the milk or very near it ; at which 

 time it is fo large and rank, and fo foon after changes its colour 

 and becomes dry, that the maggot which muft then be laid in 

 it, would not have fufficient time to compleat its growth, and 

 would therefore perifli, and in the fall of the year the infeft 

 would difappear. Others are of opinion, that there is fo 



