Application of Environmental Scanning Electron Microscopy in Distinguishing Different Instars of Chilo suppressalis Larvae in Rice

SHI Xiao-li; ZHU Feng; LIU Zhong-xian; LU Ming-xing; YANG Yang

doi:10.13651/j.cnki.fjnykj.2025.01.010

Abstract：Chilo suppressalis is one of the main pests of rice,and its damage has gradually increased in some areas of China in recent years.Due to the difficulty of the instar classification of Chilo suppressalis larvae and the lack of scientific standard for instar classification,it is necessary to further study the instar classification standard of Chilo suppressalislarvae,so as to provide scientific basis for the prediction and control of Chilo suppressalis.The experimental insect source was got from the the larvae population of Chilo suppressalis raised by the rice seedlings in indoor condition,and the overwintering larvae of Chilo suppressalis were collected from rice piles in paddy fields.By using the environmental scanning electron microscopy(ESEM)technique,the variation characteristics of the number of crochets on prolegs and head width of Chilo suppressalis larvae at different instars was studied systematically,so as to provide a basis for formulating the scientific standard for distinguishing instars of diferent instar larvae.The results showed that:the average number of crochets on prolegs of Chilo suppressalis larvae from the 1st to 6th instars was 6.2,13.0,18.4,30.0,41.0 and 49.2,respectively,while the average number of crochets on prolegs of the overwintering larvae was 41.0.At the same time,the number of crochets on prolegs of Chilo suppressalis larvae increased significantly with the increase of larval instar.And there were significant differences in the number of crochets on prolegs among different instar larvae.But the number of crochets on prolegs of overwintering larvae was not significantly different from that of the 5th instar larvae.The head capsule widths of Chilo suppressalis larvae(1st-6th instar)was broadened as the instar of the larva increased,which was 0.25 mm,0.45 mm,0.68 mm,0.98 mm,1.15 mm and 1.31 mm,respectively,while the average head width of overwintering larvae was 1.44 mm.And there were significant differences in the head width of various instar larvae,and the overwintering larvae of Chilo suppressalis had the longest head width.The number of crochets on prolegs and head width of Chilo suppressalis could be used to accurately distinguish the various instar larvae and overwintering larvae of Chilo suppressalis.Moreover,the the classification criteria for different instar larvae and overwintering larvae of Chilo suppressalis were also clarified,according to the number of crochets on prolegs and head width.