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THE EFFECT OF SPRING BURNING OF SEED ALFALFA FIELDS ON LEAF CHARACTERISTICS AND ON MANDIBULAR WEAR OF FEMALE LEAFCUTTER BEES [MEGACHILE ROTUNDATA (F.)] (HYMENOPTERA: MEGACHILIDAE)1

Published online by Cambridge University Press:  31 May 2012

B.D. Schaber*
Affiliation:
Agriculture Canada Research Station, PO Box 3000. Main, Lethbridge, Alberta, Canada T1J 4B1
E.G. Kokko
Affiliation:
Agriculture Canada Research Station, PO Box 3000. Main, Lethbridge, Alberta, Canada T1J 4B1
T. Entz
Affiliation:
Agriculture Canada Research Station, PO Box 3000. Main, Lethbridge, Alberta, Canada T1J 4B1
K.W. Richards
Affiliation:
Agriculture Canada Research Station, PO Box 3000. Main, Lethbridge, Alberta, Canada T1J 4B1
*
2Author to whom correspondence should be addressed.

Abstract

Increased seed yields often result when alfalfa fields are burned in spring. The main pollinator of seed alfalfa in Alberta is the alfalfa leafcutter bee, Megachile rotundata (F.), that cuts pieces of leaves to build thimble-like cells. One hypothesis for increased seed yield is that alfalfa leaves from burned fields may be easier for the bees to cut. Cutting of leaf pieces causes progressive wear to the mandibles, which could decrease bee efficiency, resulting in reduced pollination and lower seed yields. An image analysis method was used to measure the mandibular wear of leafcutter bees from burned and unburned alfalfa fields. No consistent difference in the amount of wear between bees foraging in burned or unburned fields was found.

Résumé

On obtient souvent des récoltes de graines plus abondantes en brûlant les champs de luzerne au printemps. Le principal pollinisateur de la luzerne en Alberta, la Découpeuse de la luzerne, Megachile rotundata (F.), découpe des morceaux de feuilles pour construire des cellules semblables à des dés à coudre. L’une des hypothèses avancées pour expliquer les récoltes plus abondantes de graines suppose que les feuilles de luzerne deviennent plus faciles à découper dans les champs brûlés. Le découpage des feuilles entraîne chez les abeilles une usure progressive des mandibules, ce qui peut en diminuer l’efficacité, et donc diminuer aussi la pollinisation et l’abondance de la récolte. Une technique basée sur l’analyse d’images a servi à mesurer l’usure des mandibules chez des abeilles découpeuses dans des champs de luzerne brûlés et dans des champs de luzerne intacts. Il n’y avait pas de différence systématique entre les mandibules des abeilles des champs brûlés et celles des abeilles des champs non brûlés.

[Traduit par la rédaction]

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1993

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Footnotes

1

Lethbridge Research Station Contribution No. 3879145.

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