Insect adaptation: unveiling the physiology of digestion in challenging environments

Insect’s resilience to adverse conditions poses a significant challenge for integrated pest control. This has resulted in huge economic losses to agriculture and forestry production as well as a range of severe ecological issues. As a physiological mechanism of insects, digestive physiology plays an important role in the process of adaptation to stress factors. However, there has been no systematic review of what stresses insects can adapt to through digestive physiology and how digestive physiology is involved in insect adaptation to stresses. In this review, the potential link between digestive physiology and adaptation of insects to biotic and abiotic stresses, including plant defense mechanisms, chemical insecticides, and entomopathogenic microorganisms, is analyzed. We point to that digestive physiology composed of digestive enzymes and gut microbial communities is an important strategy for insects to resist plant physical defense (e.g., hemicellulose, pectin, and microfibers), chemical defense (e.g., azadirachtin, diterpenoid acids, and phenolic glycosides), chemical insecticide stress, and entomopathogenic microorganism infection. In addition, the primary function of the digestive physiology in insects is to ensure energy supply during biotic and abiotic stress, assist in the metabolism of exogenous toxins (e.g., anti-insect proteins, primary metabolites, secondary metabolites, and insecticides), and improve their innate immunity against entomopathogenic microorganisms. This review is helpful to elucidate the mechanism of pest adaptation to adversity, and provide a breakthrough point for analyzing the causes of pest outbreaks.