It was hard for me not to read an article with the title, “Shakers and head bangers: Differences in sonication behavior between Australian Amegilla murrayensis (blue-banded bees) and North American Bombus impatiens (bumblebees).”
A little background first: Sonication is another term for buzz pollination. Buzz pollination is a special way that some bees get pollen from flowers. For a number of flowers, bees collect pollen sort of accidentally by just rubbing up against the flower parts naturally as they drink the flower’s nectar. They become dusted with pollen and thus collecting nectar is almost “by mistake.” The bees then use their legs to brush the pollen grains from their fur onto their back legs so that they can carry it back to the nest.
Pollen is the bees’ source of protein for feeding larvae, so that the larvae can grow into adult bees. Collecting pollen also helps the flowers, too, because any stray grains on the bee’s body that she misses can be transferred to the next flower she visits, thereby allowing for plant reproduction.
In some flowers, like tomato plant blossoms or blueberry plant blossoms, bees can’t get pollen so easily. For these types of flowers, the pollen is kept inside cone-like structures called anthers. There are pores in the anthers and somehow the bee must get the pollen out. And how do bees do this? Bumblebees use buzz pollination: they grasp the anther tip with their mandibles (mouthparts), curl their body around the anther, and hang on with their legs. It looks like this:
Then comes the cool part: The bumblebee shakes her flight muscles really fast, without flapping her wings, causing the bee and the flower to vibrate. This shakes the pollen out of the anther pores and the pollen falls onto the bee’s belly. (Think of it like shaking a tree to get the fruit to fall down.) This is called buzz pollination because when the bee shakes her flight muscles it actually makes a high-pitched buzz sound. (If you find yourself by some blueberry or tomato flowers, listen for the quick bzzzzzttt! sound of the bumblebees!) The bee can then brush the pollen from her belly onto her back legs and voila! She scored some pollen.
Honeybees have never been observed buzz pollinating flowers, so bumblebees are quite special in this regard.
Anyway, back to the article: So up until now I thought that bees buzz pollinate by using the procedure I just described: grabbing onto flower anthers and shaking like crazy! But it turns out there is a species of bee in Australia–the blue-banded bee–that does things a little differently…
The authors of the article report that they observed both North American bumblebees and Australian blue-banded bees as they pollinated cherry tomato plants. They took some high-speed videos and found that the blue-banded bees grasped the flower like bumblebees, but they didn’t grab the flower with their mandibles. Instead, when they shook their flight muscles, it caused their head to bang up against the anthers. The tapping of their head up against the anthers released the pollen.
The authors couldn’t conclude which was a more efficient way to get pollen: by shaking or head-butting the anthers. But it shows just how unique different species can be in their behaviour.
Another cool point is that little brown marks are left on the anther cone after it has been buzz pollinated. Commercial tomato growers call these marks “bee kisses,” and they are a sign that bees have visited the flowers. The authors note that the “bee kisses” left by head-butting the anthers were similar to those left by shaking.
A special note: Have you heard of neonicotinoid pesticides in the news? They are a type of pesticide that have been linked to colony collapse disorder in honeybees and to other damaging effects in bees. There is evidence that these pesticides interfere with bumblebees’ buzz pollination behaviour.
Reference: Switzer, C. M., Hogendoorn, K., Ravi, S., & Combes, S. A. (2016). Shakers and head bangers: Differences in sonication behavior between Australian Amegilla murrayensis (blue-banded bees) and North American Bombus impatiens (bumblebees). Arthropod-Plant Interactions, 10, 1-8. DOI: 10.1007/s11829-015-9407-7.