Morphological and physiological adaptations of wood-boring beetle larvae in timber

Beetles which develop boring tunnels inside and feed on seasoned wood present morphological and physiological adaptations related to the specific activities of their larvae in such a peculiar substrate. As far as protection of antiquarian goods made of wood is concerned, we are dealing mainly with three Coleoptera families, namely Lyctidae, Anobiidae, and Cerambycidae, which include species with wood-boring larvae. The adaptation to wood-boring and wood-feeding activities in beetle larvae was reached independently by phyletic lines not closely related, as a convergent evolution due to feeding behaviour. Among these adaptations, the following are examined with reference to the three families mentioned above. The conformation and activity of the larval mandibles and their possible correlations with the characteristics of the wood attacked are considered together with the presence of body structures for anchoring the larvae to the wood substrate inside the tunnel during the gnawing action. Intracellular endosymbiosis (endocytobiosis) with yeasts or bacteria, capable of supplementing larval diets lacking in some essential nutrients, and its main features are summarized. Last, structural and functional characteristics are discussed as regards tracheal spiracles, provided with filter devices important for preventing intrusion of wood powder into tracheae from larval tunnels as well as useful for avoiding dehydration.