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What makes a good pollinator?

An orchard mason bee (Osmia lignaria) with its hairs covered in pollen.
Credit: Espace pour la vie / André Payette
Mégachile des vergers ( Osmia lignaria) dont les poils sont recouverts de pollen.
What makes a good pollinator?

When we think of pollinating insects, what often come to mind are bees, bumblebees and butterflies. And yet, there are numerous other insect groups that transport pollen from flower to flower. But what makes an insect a good pollinator? There are three criteria used for determining that.

1 | Morphological features

These features include the insect’s size, its hairiness (density, length and type of hairs) and the length of the tongue. These elements make it possible to answer the question, Is this insect physically capable of transporting pollen?

  • Size: a 2-mm insect won’t be able to transport as much pollen as a 2-cm insect.
  • Hairiness: pollen can’t be transported by hairless insects, because it can’t cling to the insect. Conversely, long-haired insects like bumblebees and honeybees have bodies that accumulate pollen more easily.
  • Tongue: certain species, like Agrius cingulata, a moth in the Sphingidae family, have a long tongue that enables them to drink nectar without actually landing on the flower. They pick up less pollen than other species having a shorter tongue.

2 | Life traits (or biological traits)

Criteria such as the insect’s life cycle, its lifespan and its habitat needs are taken into account when determining which insect species visit which flowers.

  • Habitat: the insect must be present in the environment where the plant grows. If we hope to pollinate a flower grown in an agricultural environment, but the target insect can’t survive in that habitat, then it won’t be considered a good pollinator.
  • Life cycle: if the insect hasn’t yet reached maturity and is not capable of flight during the period that the target flower is in bloom, it won’t be considered a good pollinator for that species. Also, climate change is creating time lags between periods of pollinator activity and periods of plant flowering. For example, certain spring flowers are now blooming earlier, but the bees that pollinate them, such as the European orchard species (Osmia cornuta), have not adapted their own period of activity.

3 | Pollination effectiveness

This point is similar to the two previous points and can be tested in the greenhouse or laboratory. Assessments are done on whether an insect transports pollen from one flower to another, whether the pollen is actually deposited in the flower, and finally, whether fruit sets. Poorly pollinated fruit, the examples that haven’t received enough visits or enough pollen, will be misshapen.

The study of insect pollination is highly complex. There’s no perfect universal pollinator, but certain species have evolved along with specific plants, in the process creating a perfect relationship.

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