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Flower-visiting and mating behaviour of Eulonchus sapphirinus (Diptera: Acroceridae)

  • Christopher J. Borkent (a1) and Evert I. Schlinger (a2)

Acrocerid flies are often considered to be rare and their role in pollination is poorly understood. In this study, adult Eulonchus sapphirinus Osten Sacken were common on flowers of Geranium robertianum L. (Geraniaceae) in Olympic National Park, Washington, and have morphological and behavioural characteristics that indicate a dependence on floral nectar. Both males and females of this species are good potential pollinators from a behavioural standpoint. They make few revisits to individual flowers, remain highly constant to one flowering species in each nectar-foraging bout, and carry pollen on their bodies. Individuals were abundant and formed the majority of insect visitors to G. robertianum flowers. Males and females differed in their flower-visiting behaviour, with females visiting more individual flowers and doing so more slowly than males. This difference between the sexes appears to relate to mating behaviour, which takes place within the flower patches. The ramifications of the observed flower-visiting and mating behaviour for flower pollination are discussed. This study shows that based on both their abundance and their behaviour, these flies are potentially important pollinators in certain habitats.


Les mouches acrocérides sont souvent considérées comme étant rares et leur rôle en tant que pollinisateurs n’est pas très bien connu. Lors de cette étude, l’espèce Eulonchus sapphirinus Osten Sacken était très commune sur les fleurs de Geranium robertianum L. (Geraniaceae) dans le parc national Olympic, Washington, et certains caractères morphologiques et comportementaux de cette espèce, portent à croire qu’elle serait dépendante de nectar de fleurs pour son alimentation. Mâles et femelles de cette espèce ont un comportement qui pourrait faire d’eux de bons pollinisateurs. Ils visitent les fleurs à plus d’une reprise, restent fidèles à une espèce de fleur dans un site déterminé et transportent du pollen sur leur corps. Cette espèce était la plus commune parmi les insectes visitant les fleurs de G. robertianum. Il a été noté que les femelles agissaient différemment des mâles, en visitant plus de fleurs que ceux-ci et en le faisant plus lentement. Cette différence comportementale entre les sexes semble être reliée à la reproduction, qui se produit à l’intérieur des sites floraux. Les implications des comportements observés liés à la reproduction et la visite des fleurs sont discutées. Cette étude démontre que l’abondance et le comportement de ces mouches en font potentiellement d’importants pollinisateurs dans certains habitats.

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The Canadian Entomologist
  • ISSN: 0008-347X
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