+6121Ideally studies on the population dynamics of organisms should be holistic, general, precise, and realistic ( 64). Much too often, however, support for research on forest pests approximates the curve of the gradations in time and space, resulting in periodic gathering of bits and pieces of information that differ little from that gathered earlier or elsewhere (68). Therefore it is not surprising that lack of compre hensive, quantitative information on many generations of a field population has handicapped the progress of theoretical thinking on the dynamics of populations, which badly needs "more light and less heat" (86). It has been proposed that research efforts should be coordinated internationally on a few model insects in order to cope with complexity and diversity of population dynamics at a high level of efficiency (25). We consider that the larch bud moth, Zeiraphera diniana, would meet the criteria for being such a model insect (1 8).The coincidence of large-scale insect outbreaks, the availability of effective insecti cides, and economic expansion of industry and tourism after World War II pro moted several extensive control actions against such forest pests as the spruce budworm, Choristoneura fumiferana, in eastern Canada and the larch bud moth, Z. diniana, in Switzerland. Public demand to protect the subalpine larch forests in the recreation area of the Engadine (Switzerland) against the recurring defoliation by the larch bud moth triggered the present research phase. This article is the first attempt to publish the results of the research period comprehensively. In addition, information concerning previous outbreaks of Z. diniana is reviewed on a worldwide base.

Summary. Traps containing a mixture of attractants for Ips typographus also caught other species of bark beetles. The numbers of Pityogenes chalcographus, Pityogenes conjunctus, and Trypodendron lineatum were too high to be interpreted as accidental captures. The males of the polygamous P_ chalcographus were specifically attracted, indicating that the L typographus pheromone or one of its components acts as a kairomone and primary attractant for the pioneering males of P. chalcographus. Key words. Attraction; bark beetles; Ips typographus; kairomone; Pityogenes chalcographus; population aggregation pheromone; Trypodendron lineatum.Colonization of host trees by bark beetles has been divided into four phases: dispersal, selection, concentration, and establishment ~. Dispersal begins with the emergence of the beetles from brood trees or overwintering sites in the ground and ends with a response to host stimuli and/or attractive pheromones, initiating the selection of a suitable host. This second phase ends with the landing on the tree and sustained feeding in the bark. The pioneering beetles are females in the case of the so-called monogamous bark beetles, but males in the case of the polygamous bark beetles. They initiate the concentration phase by emitting their specific population aggregation pheromone, which attracts both males and females and thus concentrates the population on one or a few suitable host trees.The polygamous bark beetles, Ips typographus (L.) and Pityogenes chalcographus (L.), swarm twice a year at about the same time 2. Both infest mainly wind blown, water-stressed, diseased or otherwise weakened spruce trees (Pieea spp., mainly Norway spruce, Picea abies). It is generally thought that such trees produce primary attractants that are missing or less concentrated in healthy spruce. These substances attract the pioneering males to suitable trees where each of them bores a hole into the bark and enlarges it to a nuptial chamber. By eating some of the bark the males take up oleoresin containing monoterpenes which are oxidized to one or several substances and excreted with the frass. These substances function as the specific secondary attractants for both males and females of their species 3. In the case of L typographus the main aggregation pheromone components are 2-methyl-3-buten-2-ol and (S)-cis-verbenol 4's. They are first excreted, whereas ipsdienol, another substance produced by the male beetle s , is excreted after the nuptial chamber has been excavated and 2-3 females have entered the gallery 7. The main component of the population aggregation pheromone of P. chalcographus is 2-ethyl-1,6-dioxaspiro(4,4) nonane s.European forest entomologists consider P. chalcographus a typical 'companion' of L typographus. But while the much larger L typographus prefers the thicker bark of the lower two thirds of the stems of more than 50-year-old spruce, P.ehalcographus prefers young spruce trees and/or the crown region, i.e. the upper third of the stems and the large branches of older trees, where the bar...

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En raison de l'étendue limitée des mélézins périodiquement ravagés par la Tordeuse grise du mélèze en France, il était loisible de se demander pour quelles raisons une place avait été réservée à cet insecte dans les délibérations du colloque auquel est consacré ce numéro de la Revue forestière française.