This article published originally by WSL of Birmensdorf (Switzerland) describes the morphological, biological and ecological characteristics of Ips cembrae which can be a serious threat to Larix decidua Mill. at all stages of its development. In order to prevent, or limit, damage caused by swarms of this insect, the signs of late or early attacks are here described, to enable operators to recognize and control them from the start, as well as the methods of fight now availabile.