Termites apart, the principal insects degrading wood are coleopters (longhorn beetle, deathwatch beetle, hesperophanes, lyctus, ...). The larvae of these insects eat wood during their years of development. With the end of the larval cycle, during the pupation, they get transformed into adult insects which leave wood to reproduce. Their flight holes are the mark of the infestation.
The house longhorn beetle (hylotrupes bajulus) attacks softwood
(ex: the frame opposite).
The duration of the larval stage is on average 3 to 5 years, but depends on the conditions of temperature and moisture. The adults emerge between mid-June and end-August.
The flight holes have the form of an oval whose large axis has a length from 6 to 10 mm. The galleries are in general parallel with the wire of wood.