**3. Application of mass spectrometry imaging in entomological researches**

MSI can visualize the spatial and temporal distributions of molecules. Endogenous metabolites, exogenous metabolites, and insect-plant interactions are three main aspects of MSI application to insect tissue section for *in situ* characterization. Endogenous metabolites refer to lipids, neuropeptides, proteins, and defense compounds [32–35]; exogenous metabolites are drugs and insecticides [36, 37]; insect-plant interactions are associated with the fate of plant secondary defense compounds in insects [38]. We summarize the major applications of MSI for a better understanding of insect physiology and metabolism (**Table 1**).
