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Pollen loads and pollen diversity on bodies of Eulonchus tristis (Diptera: Acroceridae): implications for pollination and flower visitation

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

Acroceridae is a family of spider-parasitic flies that often visit flowers as adults, although little is known about their possible role as pollinators. Eulonchus tristis Loew visiting flowers of Brodiaea elegans Hoover (Liliaceae s.l.) and Iris douglasiana Herbert (Iridaceae) were collected in California. Individuals carried large pollen loads, although visitors to B. elegans carried significantly more pollen grains than visitors to I. douglasiana. Visitors to B. elegans also carried a higher percentage of focal-plant pollen (91%) than visitors to I. douglasiana (38%). There was no difference in the diversity of pollen species (approximately nine) carried by visitors to either plant species. For visitors to B. elegans, no difference was seen in the amount or diversity of pollen carried with respect to the sex of the visitor. The behaviour potentially resulting in the acquisition of these pollen loads is discussed. These results show that E. tristis has the potential to be an important pollinator for these plant species, particularly B. elegans.


Les Acroceridae sont des mouches parasitoïdes d’araignées dont les adultes visitent souvent les fleurs, bien qu’on connaisse mal leur rôle potentiel comme pollinisateurs. Nous avons récolté en Californie des individus d’Eulonchustristis Loew en train de visiter des fleurs de Brodiaea elegans Hoover (Liliaceae s.l.) et d’Iris douglasiana Herbert (Iridaceae) en Californie. Ces insectes portaient d’importantes charges de pollen, bien que ceux qui visitaient B. elegans transportaient significativement plus de grains de pollen que ceux qui visitaient I. douglasiana. Les individus qui visitaient B. elegans transportaient aussi un pourcentage plus élevé de pollen de cette plante ciblé (91%) que ceux qui visitaient I. douglasiana (38%). Il n’y avait pas de différence de diversité dans les espèces de pollen (environ neuf) transportées par les visiteurs de chacune des plantes deux plantes. Chez les insectes qui visitaient B. elegans, ni la quantité ni la diversité du pollen ne variaient en fonction du sexe. Les comportements possiblement reliés à ces charges polliniques y sont aussi discutés. Nos résultats montrent donc qu’E. tristis peut potentiellement être un important pollinisateur des ces espèces végétales, particulièrement de B. elegans.

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The Canadian Entomologist
  • ISSN: 0008-347X
  • EISSN: 1918-3240
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