For humans the insect is completely harmless. Females have a long, thin, saw-like, but very strong ovipositor at the underside of their abdomen. It is used to drill the wood of coniferous trees where they lay their eggs in those small bore holes. The economic damage caused thereby is however relatively small and is pretty often only noticeable once the wood is processed and installed. The development of the larvae can take more than four years, so that one or the other Blue Horntail might appear in a sitting-room or under the textile of a new wooden bench after hatchig from the egg.