has_part membrane chitin peritrophic membrane CLAO:0001217 BTO:0001038 A delicate, cylindrical sheath of chitin continuously secreted from the posterior edge of the foregut of insects and millipedes that ingest solid food, which surrounds the food as it passes through the midgut. https://www.ebi.ac.uk/ols/ontologies/BTO/terms?obo_id=BTO:0002316