New results concerning the breakdown of wool by moth and beetle larvae

Abstract

Some insect larvae have a remarkable ability to digest and utilise keratin, i.e. highly cross-linked protein material. Extensiue investigations about the digestive mechanism of these insects have already been carried out but the actual course of keratin digestion by the insect pests is still under discussion. Inuestigations of moth and beetle excreta by amino acid analysis and polyac ylamide gel electrophoresis should shed more light on this subject. The present paper describes such comparative studies of larval faeces excreted afterfeeding with non-mothproofed and mothproofed wool, using low concentrations of two stomach poisons as moth-and beetle-proofing agents. It has been found by amino acid analysis that all excreta examined contained a mixture ofpeptides and free amino acids. Most ofthe moth excreta were rich in free cystine and histidine whereas the beetle excreta contained much free cystine and arginine. Only the brown house moth (Hofmannophila) proved exceptional in this respect. Gel electrophoretic analysis of excreta proteins showed a different pattern of breakdown of wool proteins by the principal wool pests. The electrophoretic patterns permitted a differentiation between the types of larvae.

Identification of isopeptidase activity in the midgut of insects: Purification, properties and nutritional ecology of a Hofmannophila pseudospretella (Lepidoptera: Oecophoridae) larval enzyme

“…The larvae of the brown house moth, Hofmannophila pseudospretella (Stainton) (Lepidoptera: Oecophoridae), are keratinophagous (Christeller et al , 1994) and a major pest of wool. Unlike other keratinophagous larvae, they excrete large amounts of cysteine in their frass (Hammers et al , 1987), suggesting that they are able to uniquely digest the high sulphur fractions of wool, the cuticular layers, the same fractions where isopeptide bonds are abundant. Because these larvae are able to utilize wool as a dietary source and isopeptide bonds are important in wool structure, we attempted to detect the presence of isopeptidase in the midgut of H. pseudospretella larvae.…”