The insect gut contains a complex and diverse microbial community, and the composition of the insect gut microbial community is influenced by multiple factors such as the host’s genetics, dietary habits, and the external environment. The host’s immune system maintains the stability and balance of the microbial community through a number of mechanisms. The microorganisms in this community play key roles in the nutrient metabolism, detoxification, immune regulation, development, and behaveior of insects. In recent years, the relevant literature has reported advances in the study of insect gut microbes, indicating the potential applications of insect gut microbes in several fields. The aim of this review is to provide a comprehensive overview of the current information on the structure of insect gut microbial communities and complex host–microbe–environment interactions. The diversity of insects’ gut microbial communities and the functions of their gut microbes are revealed. By studying insect gut microbial communities, we can gain insights into the functions of these microbes in the host and explore the causal relationships between them and the host’s physiology and behavior. This will not only help us to understand the mechanism of action of the microbiome, but also provide a basis for the development of innovative biotechnology based on insect gut microbes. This research has significant theoretical value in academia and also has a wide range of applications in agriculture, environmental protection, industrial production, and healthcare.

Despite the huge human and economic costs of invasive insects, which are the main group of invasive species, their environmental impacts through various mechanisms remain inadequately explained in databases and much of the invasion biology literature. High-throughput sequencing technology, especially whole-genome sequencing, has been used as a powerful method to study the mechanisms through which insects achieve invasion. In this study, we reviewed whole-genome sequencing-based advances in revealing several important invasion mechanisms of invasive insects, including (1) the rapid genetic variation and evolution of invasive populations, (2) invasion history and dispersal paths, (3) rapid adaptation to different host plant ranges, (4) strong environmental adaptation, (5) the development of insecticide resistance, and (6) the synergistic damage caused by invasive insects and endosymbiotic bacteria. We also discussed prevention and control technologies based on whole-genome sequencing and their prospects.