Abstract: The symbiotic relationship between endosymbionts and their insect hosts is ubiquitous in nature, and they are interdependent, interacting and coevolving. In recent years, studies on insect endosymbionts mainly focus on hemipteran and dipteran insects. However, a growing number of studies show that the interaction mode and mechanism between lepidopteran insects and their endosymbionts are also attracting more and more attention. Lepidopteran insects are widely distributed and play important roles in the ecosystem as herbivores and pollinators, and most of their larvae can cause great economic losses to the agricultural and forestry production. The diversity of endosymbiont community in lepidopteran insects is relatively low, which is mainly dominated by secondary symbiont Wolbachia. A few species are also infected with Spiroplasma, Arsenophonus and Rickettsia. These endosymbionts are mainly transmitted maternally from mother to offspring, whereas their horizontal transmission may also be occurring in nature. And they play important roles in the growth and development, reproductive manipulation, environmental adaptation and genetic evolution of hosts. Nowadays, diagnostic polymerase chain reaction (PCR), high-throughput amplicon sequencing, and metagenomic sequencing are generally used to detect endosymbionts. However, there are still some difficulties in the research of endosymbionts in lepidopteran insects, including that most endosymbionts can not be cultured in vitro, and the biological functions of endosymbionts with low abundance are difficult to be determined. Considering the distribution of endosymbionts and difficulties in lepidopteran insects, it is suggested that future research should focus on secondary symbionts and their biological functions.

Key words:  Lepidoptera, endosymbiont; Wolbachia, Spiroplasma, transmission mode, biological effect, symbiotic relationship