The adults hatch normally in the early of May,the adult population density can be affected by rainfall,the high density occurred in wet year,low density occurrs in dry year especially dry Spring season.

• 正常年份5月上旬成虫羽化,降雨量的大小可以直接影响发生量,多雨湿润的年份发生量大,干旱少雨的年份尤其是春季干旱可以明显降低虫口数量。