Cellulose digestion in insects

1. 1. Cellulose digestion has been demonstrated in the Thysanura (Lepismatidae), Orthoptera (Cryptocercidae, Blattidae). Isoptera (Mastotermitidae. Kalotermitidae. Hodotermitidae, Rhinotermitdae, Termitidae). Coleoptera (Buprestidae. Anobiidae, Scarabaeidae, Cerambycidae), and Hymenoptera (Siricidae). 2. 2. In all but the scarab beetles, cellulose digestion is brought about by a complex of three types of enzymes (C 1-cellulases, C x-cellulases, and cellobiases), as in fungi. 3. 3. Many insects are able to synthesize their own C x-cellulases and cellobiases, but few (if any) can synthesize C 1-cellulases. 4. 4. Insects compensate for their inability to synthesize C 1-cellulases by exploiting the cellulolytic potential of protozoa, bacteria, or fungi. 5. 5. The maintenance of permanent populations of hindgut protozoa, the maintenance of permanent populations of hindgut bacteria, and the ingestion of fungal cellulases are described as three distinct mechanisms by which insects have been shown to use the cellulolytic potential of microorganisms. 6. 6. A process in which ingested cellulolytic bacteria proliferate in one region of the gut at the expense of ingested cellulose, only to be digested and assimilated in a more posterior section, is a fourth possible mechanism by which insects might accomplish the digestion of cellulose with the help of microorganisms.