Response of the common cutworm Spodoptera litura to zinc stress: Zn accumulation, metallothionein and cell ultrastructure of the midgut

► A dose-response was observed between Zn accumulations in S. litura larvae midgut and Zn concentrations in diet. ► Metallothionein in midgut of S. litura larvae was positively correlated with Zn accumulations in the midgut. ► Numerous electron-dense granules and vacuoles appeared in cytoplasm of the midgut from Zn stress treatments. ► MT induction and EDGs are the effective detoxification mechanisms for S. litura larvae to protect against heavy metals.