Tannin-Insect Interactions

Abstract

Significant evidence exists that dietary tannin can reduce growth and fecundity of some insect species. However, few studies have identified clear physiological or toxicological impacts of tannins on insect herbivores; some have suggested that tannins are positive nutritional factors. Insect species that feed on tanniniferous plant tissues often appear able to tolerate dietary tannins and may even be stimulated to feed by their presence. Alkaline midgut pH, surfactants, and the peritrophic membrane all may help these species tolerate moderate tannin concentrations in the diet. Reduced growth of adapted species at high tannin concentration may represent metabolic costs, not direct tannin effects. New evidence suggests an important impact of dietary tannin on microbial enemies of insects. The study of tannin-insect interactions has been hampered by poor communication between chemists and biologists.