Beetles as Pollinators

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December 5, 2020
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Beetles as Pollinators

Beetles often bury themselves deep in flowers. This is Brachyleptura rubrica peeking over the edge of a Hydrangea quercifolia flower cluster.

Beetles often bury themselves deep in flowers. This is Brachyleptura rubrica peeking over the edge of a Hydrangea quercifolia flower cluster.

While bees and butterflies are the pollinator darlings, beetles also provide essential pollinator services and deserve a little more respect.

Beetles are fascinating and easy to observe, being colorful (usually) and relatively sedentary. Beetles (Coleoptera) were some of the first pollinators, having evolved with early flowering plants long before bees appeared. Globally, double the number of beetle species visit flowers compared to all bees and butterflies combined! While few plants rely exclusively on beetles for pollination, a large percentage of the world’s flowering plants benefit from beetle pollination.
Beetles mostly visit flowers to eat pollen (a protein) instead of nectar like most other pollinators. They have a “bad reputation” as pollinators because they eat plant tissue including the flower. But beetles evolved with chewing mouthparts and its part of their nature. Pollinating beetles mostly walk around flowers, picking up pollen that sticks to their bodies, and “incidentally” depositing it on the flower’s stigma to complete pollination. When beetles are ready to move to another flower or plant, they often walk to a convenient flight pad first. They may pause to eat or remove pollen that has stuck to their antenna or legs. Then they raise their elytra, unfold their hindwings, and lift into flight. This happens slow enough for the human eye to follow.
Video: Shining flower beetles can make a flower head shimmer with reflections as they run around eating pollen.
Beetles visit flowers of diverse woody and herbaceous plants species, but most frequently pollinate flat wide flower heads (umbels) and bowl-shaped flowers. These shapes provide easier access as they aren’t the most skilled fliers. They are also said to prefer flowers with odors – not necessarily those that humans consider attractive. To search out beetles, look for them on their favorite flowers including native hydrangeas, roses, goldenrods, magnolias, and water lilies.

See the photo gallery below for beetles and the flower species I have found them on.

Modern-day beetles have a particular affinity to the close descendants of the ancient flowering plants (cycads) they evolved with, primarily plants in the Magnoliids superfamily like magnolias, pawpaws, and sassafras. Magnolia trees are pollinated almost exclusively by beetles. The flowers are large, fragrant, and bowl-shaped with a simple structure. The plant has evolved defenses against the beetle with tough petals, lots of pollen, and heavily protected seeds.
Many pollinating beetles are common, beautiful, and easy to recognize. Beetle bodies have a simple stream-lined appearance because their hardened forewings, called elytra, cover their hindwings and abdomen for protection. Their antennas range from stumpy clubs, to flamboyant combs, and long slender “horns” that can be longer than their bodies. They have intriguing family names, but many species lack common names. Pollinating beetle families include: soldier, blister, long-horned, checkered, tumbling flower, soft-winged flower, scarab, false blister, and rove.
Flower Longhorns are one of my favorite pollinating beetle families. So far, I’ve had 8 species in my yard. They have slender colorful or patterned bodies with long elegant antenna – not horns. At times, their bodies can get so covered in pollen from crawling through the flowers you can’t tell what species they are.

Enjoy discovering the pollinating beetles in your yard and parks. And if your favorite beetles don’t have a common name, make one up for yourself!

Beetle Pollinator and Flower Slideshow
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