Digestion of structural components of the wool fibre in the alimentary system of Anthrenus flavipes larvae has been studied by optical and scanning electron microscopy. The larvae have been shown to bite off wool fragments of varying length ranging from 20 to 100-mu-m which rapidly pass through the foregut and accumulate in a large sac-like midgut. Digestion of outer cuticular scales occurs in the midgut region. Large numbers of symbiotic bacterial cells facilitate extensive digestion of keratin fibrils of the cortex in the ileum region, resulting in complete structural disintegration of the wool fibre. Actively feeding amoeba-like protozoans gradually replace the bacterial flora in the posterior ileum and rectum regions. Digested wool components and microbial biomass gradually become compact due to absorption of nutrient fluid in the hindgut. In the final stage of digestion, the compact faecal pellets consisting of remaining undigested and partially digested wool fragments and the microbial biomass, containing mainly protozoans and lysed and intact bacterial cells, lie in a chain in the rectum before excretion.