Objective To explore the adaptive mechanisms of Endoclita vietnamensis larvae to different host plants with varying degrees of preference, clarify the co-evolutionary relationship between herbivorous insects and their host plants, and provide a theoretical basis for the green control of this pest.

Method Three host plants with different levels of palatability - Eucalyptus grandis × E. urophylla (high palatability), Mallotus apelta (medium palatability), and Broussonetia papyrifera (no palatability) were selected as study subjects. The physical and chemical properties of the host plants and the physiological responses of the larvae following feeding were measured. Larval feeding rate and survival rate were statistically analyzed, and the potential correlations among the indicators were explored through correlation analysis.

Result (1) The analysis of the physical and chemical properties of the host plants showed that the content of reducing sugar and soluble sugar in the bark was the key factor affecting the host selection of the larvae, and the content was in the order of E. grandis × E. urophylla > M. apelta > B. papyrifera, which was completely consistent with the order of larval preference; (2) Flavonoids, as the core defense substances of the host plants, were significantly induced to accumulate after larval feeding, but their content was significantly positively correlated with the larval feeding rate, indicating that the larvae had developed an effective tolerance mechanism; (3) Larvae dynamically regulated their enzymatic systems to adapt to a multi-host environment: protective enzymes (SOD, CAT) were continuously activated, detoxification enzymes (AchE, GST) reached their peak in the middle of feeding, and protease activity was significantly down-regulated; (4) Correlation analysis confirmed that the larval feeding rate was significantly positively correlated with the content of reducing sugar in the host bark, and significantly positively correlated with the content of soluble sugar, flavonoids, and the activity of AchE in the larvae themselves.

Conclusion The larvae of E. vietnamensis adapt to multiple hosts by perceiving sugar signals from the hosts and dynamically regulating the enzyme system. This study provides a theoretical basis for understanding the co-evolution of insects and plants and the green control of pests.