Estimating the number of spruce bark beetles (Ips typographus L.) emerging through the same exit hole. A factor of importance for populalation estimates

agentes nocivos animal animal nuisible animales animales nocivos animals arthropode arthropods coleoptera dynamique des populations escarabajos de la corteza facteur nuisible injurious factors insecte insecte nuisible insectos insects invertebrados invertebrates ips noxious animals organisme nuisible pest insects pests plagas population population density population dynamics scolyte