Interaction and co-evolution among parasites, host insects, and gut microbiota.

Insects, the most diverse group of animals, inhabit almost all environments on Earth. They are susceptible to a wide range of parasites, including entomopathogenic protozoans, nematodes, and ectoparasitic mites. These parasites manipulate host physiology via immunomodulation, endocrine disruption, and metabolic reprogramming. The long-term coexistence of insects and parasites has driven the evolution of intricate survival strategies. Insects deploy morphological, physiological, and behavioral adaptations to mitigate infection risks, whereas parasites counter with sophisticated mechanisms enhancing transmission and reproductive success. Emerging evidence indicates symbiotic microbiota as critical mediators in this evolutionary arms race, modulating infection outcomes through microbial-host-parasite crosstalk. Here, we review recent research progress on the effects of parasites on the development, reproduction, immunity, and behavior of insect hosts; the evolutionary dynamics between insects and parasites; and the interactions of host-parasite-microbiota in insects. Compared to mammals, insects provide a simple model system for elucidating conserved molecular mechanisms underlying host-parasite-gut microbiota interactions. This paradigm not only advances fundamental understanding of evolutionary parasitology but also pioneers microbial-based biocontrol approaches, offering sustainable alternatives for agricultural pest management and economic insect conservation.