ABSTRACT.Parts of the posterior caeca ofSchistocerca gregariaForskål are complexly pocketed and the whole caecal lining including the pockets secretes a peritrophic membrane. Such pockets are not present in six other species of Acrididae examined. Preliminary experimental evidence, based on absorption of ingested dyes, suggests that the presence of pockets is related to rapid water absorption and perhaps to sequestering plant toxins ingested in a very polyphagous diet