Abstract: Interactions between endosymbionts and their insect host have drawn much attention at present. Endosymbionts could facilitate their hosts to acquire additional nutrition, protect them from natural enemy and enhance their insecticide resistance. Their special roles include facilitating digestion of food or providing nutrients that were limited or lacking in the host diet, enhancing pathogen and parasitoid resistance through secretion of antimicrobial peptides or toxin and strengthening resistance of their hosts by regulating physiological reaction and accurate expression of resistance genes. These facts strongly suggest that endosymbionts play an important role in regulating host development through mediating the biological characters to expand the host’s ecological niche. The functions of endosymbionts were analyzed through examination of changes in biological characters of host before and after infection. Recently, new techniques on transcriptomics, proteomics and genomics have promoted the research on mutualism mechanisms between symbionts and insect hosts. This will not only reveal the endosymbionts and their functional genes on host reproduction, survival, population dynamics and adaption to the environment, but also open new insight into potential biological roles of endosymbionts, providing new insight for biological control of pest insect.

Key words: Insect, endosymbiont, primary endosymbiont, secondary endosymbiont, mutualism, biological characteristics, metagenome