What makes bumblebees such good pollinators?

Bumblebees are excellent pollinators of many crops and wild plants. Without them our landscape would be starkly different, and far less colourful. So what makes them such good pollinators?

1. Bumblebees have dense hairy bodies and if you look at their hairs under a microscope you will see that they are actually forked at the tip. This makes them great at gathering and transporting the textured pollen that insect-pollinated plants produce.

2. Tongue length. Some bumblebee species have short tongues, while others have long tongues. Short-tongued bumblebees have adapted to forage on flowers with short corollas (the tube leading to the nectar), whereas long-tongued bumblebees are more specialised and are adapted to feed from generally more complex flowers with long corollas. This means that bumblebees as a group of insects can utilise and pollinate a wide array of different flower types.

3. Buzz pollination. If the first two points weren’t enough to crown the bumblebee a master pollinator in the realm of insect pollinators, they have one other trick up their proverbial sleeves. Bumblebees are able to ‘buzz pollinate’.

The following clip shows bumblebees buzz pollinating Opium poppies. Be sure to turn up the sound and you will hear that glorious buzz as the bumblebees release the pollen from the anthers, rewarded for their efforts by the protein-rich pollen.

So, what is buzz pollination?

Some flower species have evolved to be conservative with their pollen, which is a very clever evolutionary strategy. Pollen is costly for the plant to produce in terms of energy, so the plant wants to be sure that the pollen produced is transported effectively in order for it to be able to reproduce. Plants that have evolved this strategy have poricidal anthers, which means that the pollen is packed tightly into the anther (the part of the plant that holds the pollen).

Most insects are unable to access this pollen, however bumblebees are able to contract their flight muscles, which produces strong vibrations that they direct on to the anther using their legs and mouth parts, resulting in a bee-covering explosion of nutritious pollen grains from the tip of the anther. The bee will comb most of these pollen grains from her fur and into her pollen baskets on her hind legs, but a few lucky grains will be missed and will go on to fertilise one of the next flowers she visits. For some unknown reason honeybees are unable to do this. Blueberries, tomatoes, aubergines and kiwis are just some examples of the many plant species that require this form of pollination. Thank you bumblebees!

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