Glycogen phosphorylase is the key enzyme to degrade glycogen,which is an important energy source.To investigate the relationship between glycogen phosphorylase and diapause as well as cold hardiness in Ostrinia furnacalis(Guenée)larvae,we cloned the glycogen phosphorylase gene(Ofgp),and described its expression pattern.The open reading frame(ORF)of Ofgp was 2526 bp,encoding 841aa.The three dimensional structure showed 33 α-helixes and 24 β-sheets,.Quantitative real-time PCR showed that the expression levels of Ofgp varied significantly in the 2nd-5th larval instars under both long and short day photoperiods and was maintained at a low level during the pre-diapause phase,followed with a sharp increase at about 36 d under short day photoperiod.For the larvae reared under long day photoperiod,Ofgp expression was highest in the haemolymph.Under short day photoperiod,the highest level was in the fat body and declined significantly in the other tissues.In addition,we found that the expression levels of Ofgp increased linearly from Octoberto January,but decreased significantly in February.The dynamics were negatively correlated with the changes of the environmental temperature.In conclusion,the expression of Ofgp in O.furnacalis larvae was significantly influenced by the short day photoperiod and lower temperature; the higher expression level of Ofgp may enhance the cold hardiness of the diapausing larvae.