Quantitative observation of the foraging tunnels in Sitka spruce and Japanese cypress caused by the drywood termite Incisitermes minor (Hagen) by 2D and 3D X-ray computer tomography (CT)

Abstract

Abstract The cryptic lifestyle of drywood termites makes it difficult to study their foraging behaviour and to detect infestations in hidden regions. In the present research, computer tomography (CT) scanning images were collected over a 1-year observation period of drywood termite Incisitermes minor (Hagen) in order to understand its foraging behaviour and, perhaps, to be able to detect the infestation as early as possible. Sitka spruce and Japanese cypress woods were the test objects. As CT scanning results show, foragers caused distinguished tunnelling patterns based on the physical properties of wood during gallery construction. The foragers primarily excavate along the earlywood in radial direction towards the outer surface of the wood to establish the primary and satellite chambers, followed by mainly superficial (0.3–3.0 cm under the surface) longitudinal expansion with occasional lateral deviations. The development of tunnelling is affected by the physical constraints of knots with their high density, high extractive and lignin contents, reaction wood (compression wood) and wood damage caused by wind.