Digestive physiology mediates the adaptation of phytophagous insects to host plants. In this study, the digestive characteristics of Hyphantria cunea larvae feeding preferences on different host plants were investigated. The results showed that the body weight, food utilization, and nutrient contents of H. cunea larvae feeding on the high-preference host plants were significantly higher than those feeding on the low-preference host plants. However, the activity of larval digestive enzymes in different host plants presented an opposite trend, as higher α-amylase or trypsin activity was observed in the group feeding on the low-preference host plants than that feeding on the high-preference host plants. Upon treatment of leaves with α-amylase and trypsin inhibitors, the body weight, food intake, food utilization rate, and food conversion rate of H. cunea larvae significantly decreased in all host plant groups. Furthermore, the H. cunea comprised highly adaptable compensatory mechanisms of digestion involving digestive enzymes and nutrient metabolism in response to digestive enzyme inhibitors. Taken together, digestive physiology mediates the adaptation of H. cunea to multiple host plants, and the compensatory effect of digestive physiology is an important counter-defense strategy implemented by H. cunea to resist plant defense factors, especially the insect digestive enzyme inhibitors.

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.