Abstract: Insulin is a protein hormone with small molecular weight and secreted by insulin cells, regulating the metabolism of sugar, fat and protein by signaling pathways, and finally affecting organisms. The insulin signaling pathways present in insects and regulate the metabolism, growth and development, and lifespan, being highly homologous with those in vertebrates. Research on insulin signaling pathways in Drosophila melanogaster and Caenorhabditis elegans can be used as a probe in life science research to supply a test model for the study of human insulin-related diseases, which is of great significance to life science research, so the research on insulin in nematodes and insects is relatively in-depth. Entomopathogenic nematodes (EPNs) are important biocontrol factors, and their life cycle includes both the parasitism stage in host insects and the free life stage in nature. During the parasitism stage, the symbiotic bacteria carried by nematodes mainly act in the blood circulation system of host insects, resulting in the death of host insects. Therefore, there is a close relationship between EPNs and the blood system of host insects, thus the effect of insulin on EPNs must be studied on both nematodes and host insects. In order to scientifically and systematically investigate the effects of insulin on EPNs and conduct indepth discussions, in this article we reviewed the physiological functions of insulin/insulin-like growth factors in insects and nematodes, so as to shed more lights on the theoretical basis for studying the effects of insulin on EPNs and the application of insulin, and insulin intervention in the application of EPNs.

Key words: Insulin, insects, nematodes, entomopathogenic nematodes, symbiotic bacterium, physiological metabolism