A STUDY OF THE FOOD RELATIONS OF THE LYCTUS POWDER‐POST BEETLES

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Abstract
SUMMARY: The histology of the larval gut of Lyctus is described: owing to the absence of salivary glands and caeca, the digestive juices must be secreted by the midgut with doubtful contribution from the hindgut. The mycetomes contain organisms which are apparently not symbiotic in relation to digestion. The skeletal substance of wood passes through the larval gut unaltered, nourishment being derived from the cell contents. A substance, soluble in water at 60o C, is necessary in oak sapwood for normal larval development. Larvae are unable to develop in wood from which starch is absent. Larvae living in wood containing relatively little starch may take two years to complete their development, instead of the normal one year. Enzymes capable of hydrolysing starch, maltose, sucrose, lactose and protein were detected in tissue suspensions of the gut and its contents. By feeding larvae on artificial diets it has been shown that starch, sugars and protein are necessary constituents of the larval food. Furthermore, larvae have been reared to the imaginal stage on a substrate which contains no wood. The ability of the female beetles to determine the suitability of wood for larval development is demonstrated and the importance of the so‐called “tasting” marks discussed. An account is given of the occurrence of starch in timber and the difficulties involved in its estimation and removal from the wood.