Palisade mesophyll tissue removed from mature leaves ofPhaseolus lunatusL. by the leafmining herbivoreLiriomyza trifolii(Burgess) was replaced with photosynthetically active cells, permitting virtually complete recovery from injury. No significant differences in biomass production or levels of ribulose-1,5-bisphosphate carboxylase were observed between damaged and control plants. Decreases in photosynthesis did not exceed 10% for leaves with approximately one-fourth of the leaf area mined. Development of other, photosynthetically inactive callus cells along vascular bundles and frass deposits served to compartmentalize leafmines, generating a suitable microclimate for regeneration of cells as well as preventing intrusion of disease inoculum and arthropod pests. Such cellular regrowth not only benefits the host, but provides substantial advantages for facultatively cannibalistic larvae that are incapable of relocating to undamaged leaves.