The peritrophic matrix is a chitin-protein structure that envelops the food bolusin the midgut of the majority of insects, but is absent in some groups whichhave, instead, an unusual extra-cellular lipoprotein membrane named theperimicrovillar membrane. The presence of the perimicrovillar membrane (PMM)allows these insects to exploit restricted ecological niches during all lifestages. It is found only in some members of the superorder Paraneoptera and manyof these species are of medical and economic importance. In this review wepresent an overview of the midgut and the digestive system of insects with anemphasis on the order Paraneoptera and differences found across phylogeneticgroups. We discuss the importance of the PMM in Hemiptera and the apparentconservation of this structure among hemipteran groups, suggesting that thebasic mechanism of PMM production is the same for different hemipteran species.We propose that the PMM is intimately involved in the interaction with parasitesand as such should be a target for biological and chemical control of hemipteraninsects of economic and medical importance.
