Dispersal by flight is obligatory for bark beetles in the subfamily Scolytinae. Adult bark beetles must leave the natal host and fly to seek new hosts for brood production. Because of the eruptive nature of some bark beetle populations, dispersal capacity has implications for beetle spread and invasion across the landscape. Bark beetle dispersal can occur over short distances within a stand or over long distances above the forest canopy, where wind aids dispersal. Despite the obvious importance of dispersal for predicting population spread, knowledge gaps in understanding factors that influence bark beetle dispersal remain. In this review, we synthesize information on bark beetle flight to gain a better understanding of this important life history trait. We assess the impact of genetic, physiological, and morphological traits on flight in different bark beetle species. We also consider the impact of abiotic and biotic environmental conditions on flight. We discuss how measurements of these factors could contribute to the development of comprehensive models to better predict spread of bark beetle populations. Through the synthesis of flight research on a variety of bark beetle species, this review provides suggestions for future avenues of research on this important aspect of bark beetle ecology.Résumé : Le vol est le moyen de dispersion obligatoire chez les scolytes dans la sous-famille des Scolytinae. Les scolytes adultes doivent quitter l'hôte où ils sont nés et s'envoler pour chercher de nouveaux hôtes afin d'assurer leur progéniture. À cause de la nature éruptive de certaines populations de scolytes, la capacité de dispersion a des répercussions sur la propagation et l'invasion de l'insecte dans le paysage. La dispersion des scolytes peut survenir sur de courtes distances à l'intérieur d'un peuplement d'arbres ou sur de longues distances au-dessus du couvert forestier où le vent favorise la dispersion. Malgré l'importance évidente de la dispersion pour prédire la propagation de la population, il y a encore des lacunes dans les connaissances concernant la compréhension des facteurs qui influencent la dispersion des scolytes. Dans cette revue de littérature, nous résumons l'information sur le vol des scolytes pour avoir une meilleure compréhension de cet aspect important du cycle vital. Nous évaluons l'impact des traits génétiques, physiologiques et morphologiques sur le vol chez les différentes espèces de scolytes. Nous discutons de la façon dont la mesure de ces facteurs abiotiques et biotiques pourrait contribuer au développement de modèles complets pour mieux prédire la propagation des populations de scolytes. Par le biais de la synthèse de la recherche sur le vol chez une variété d'espèces de scolytes, cette revue de littérature fournit des suggestions pour de futures avenues de recherche sur cet aspect important de l'écologie des scolytes. [Traduit par la Rédaction]

Flight polyphenisms naturally occur as discrete or continuous traits in insects. Discrete flight polyphenisms include winged and wingless morphs, whereas continuous flight polyphenisms can take the form of short- or long-distance fliers. The mountain pine beetle (Dendroctonus ponderosae) exhibits polyphenic variation in flight distance but the consequences of this flight variation on life history strategies of beetles is unknown. This study assessed the effect of flight on two particular aspects of beetle biology: (1) an energetic trade-off between flight distance and host colonisation capacity; and (2) the relationship between flight distance and pheromone production. A 23-h flight treatment was applied to a subset of beetles using computer. After flight treatment, both flown and unflown (control) beetles were given the opportunity to colonise bolts of host trees, and beetles that entered hosts were aerated to collect pheromone. A trade-off occurred between initiation of host colonisation and percent body weight lost during flight, which indicates energy-use during flight affects host acceptance in female mountain pine beetles. Furthermore, production of the aggregation pheromone trans-verbenol by female beetles was influenced by both percent weight lost during flight and flight distance. Male production of exo-brevicomin was affected by beetle condition following flight but not by the energy used during flight. These novel results give new insight into the polyphenic flight behaviour of mountain pine beetles. Flight variation is adaptive by acting to maintain population levels through safe and risky host colonisation strategies. These findings suggest mechanisms that facilitate the extremities of the continuous flight polyphenism spectrum. These opposing mechanisms appear to maintain the high variation in flight exhibited by this species.

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