sentence: Eggs used in this experiment were taken from the G. molesta colony , which was maintained on an artificial diet for more than 6 years at 26 ± 0.5 ° C 70 ± 10 % relative humidity ( RH ) with a photoperiod ( L :D ) of 15 h :9 h in the Integrated Pest Management Laboratory of Northwest A & F University in Yangling , Shaanxi , China .