Studies on the Digestion of Cellulose by the Larvae of the Eucalyptus Borer, Phoracantha semipunctata (Coleoptera: Cerambycidae)

Abstract

Larvae of the native Australian xylophagous insect P. semipunctata, the adults of which lay eggs only on Eucalyptus species, penetrate the bark, then the phloem and feed at the boundary between the phloem and the xylem, causing deep furrows. As the phloem dries, they penetrate the xylem, which they damage by the formation of galleries. Digestion of wood is facilitated by glycosidases acting not only on oligosaccharides but also on many polysaccharides, notably starch, various hemicelluloses and cellulose. The role of a cellulase produced by the midgut epithelium of the larvae was examined and the characteristics of a partially purified preparation of this enzyme from the midgut epithelium studied. The enzyme was shown to have a molecular weight of less than 34500 and to hydrolyse carboxymethylcellulose and Cellulose-Azure: It was identified as being an endo-ft-l,4-glucanase.