g8 Ohfervations on the Hejfian Fly. 



render this time fo various, that fome will be full grown, and 

 others transformed into a chryfalis, whilft others are fmall ; and 

 this circumftance has no doubt led many fkilful obfervers to 

 fuppofe, that there are two complcat generations of the infeft 

 before harvelt. From this account of the maggot it will be 

 obvious, that this is the flate in which the infeB: deftroys the 

 grain ; for as foon as it has obtained its growth, it is transformed 

 into a chryfalis of a dark brown colour, in which ftate it requires 

 no further nourifhment, and appears then to do no other 

 mifchief to the grain, than what may arife from indenting the 

 ftraw. The chryfalis is the fecond flate, or mode of exifterice, ■ 

 which the infecl affumes, and is that in which it is moftly 

 obferved. It is found in this ftate in the time of harveft, and 

 when the grain is gathered, remains in the ftubble until it is 

 transformed into a fly : But to this there are fome few excep- 

 tions; for thofe which are fometimes in the upper joints, and 

 may happen to be fo high as to be above the fickle or cradle 

 •when the grain is gathered, will of courfe be gathered with it, 

 and muft always go with the ftraw, becaufe they adhere too 

 clofely to it, to be beaten, or threfhed off, without being 

 defiroyed. The length of time for which the infeft will continue 

 a chryfalis in the fummer feafon, is no doubt regulated in a 

 great degree by the quantum of heat which it may enjoy in that 

 fituation. For this reafon it is very probable, that in diffej-ent 

 parts of the country, and in different expofures to the fun, this 

 period of time may vary very confiderably ; but though different 



