Pollinators aid in the successful reproduction of nearly 75% of flowering plants, plants whose capacity to reproduce is either entirely dependent on this animal-assisted service, or whose productivity is substantially increased when pollinator communities are present. Aptly named after this essential ecosystem service, pollinators are vectors in the transfer of pollen from one plant to another of the same species, in a sort of accidental mutualistic relationship, or a relationship that is beneficial to both the pollinator and the flower. Bumble bees, specifically, visit flowers to collect nectar and pollen resources for themselves and their colony, and while their intention is not to help flowers, the plant’s reproductive success is benefitted when pollen is moved from flower to flower as a side effect of this foraging behaviour. Nature works in pretty interesting ways sometimes, doesn’t it?

Visual representation of the three major steps of animal-assisted pollination. Photo © Little Bumblebees, https://sites.google.com/site/littlebumblebees15/

There are many types of animal pollinators, including bees, butterflies, flies, and beetles, but some of the most effective pollinators in our Canadian landscapes are our bumble bees! But what makes them so effective compared to some other insect pollinators? Here are four easy-to-see characteristics that make bumble bees one of the best-suited insects to get the job of pollination done!

1. They have big, hairy bodies!

One of the most noticeable physical traits of bumble bees is how big and hairy they are. Bumble bees are some of the largest bees and are covered in thick hair, and together this makes them great pollinators, without even trying! Bumble bees accumulate a positive electric charge on their hairs as they fly. But wait, who cares about that? We all build up charge on our bodies as we walk… Well, pollen is negatively charged making it electrostatically attracted to the bee, so pollen grains get stuck more readily all over their positively-charged, hairy bodies, and are transferred from flower to flower while the bee forages for pollen and nectar. Being big also means that there is more surface area that contacts the flowers and picks up pollen, especially if they have to squeeze themselves deep into a tight cone-shaped flower to access the nectar source!

A yellow-banded bumble bee (Bombus terricola) queen covered in dandelion (Taraxacum officionale) pollen grains and with full pollen loads in the corbicula, or pollen basket, of her hind legs! Photo © T. Harrison

2. They are biologically adapted to our Canadian climate!

Bumble bees make for good pollinators because they’re tolerant of our Canadian climate—which is more than a lot of us Canadians can say! The bumble bee’s size and hairiness doesn’t only make it better at collecting and transferring pollen passively, these are also characteristics that help to keep it warm. Aside from the hairs acting as natural insulators, a bumble bee’s large body size makes for large flight muscles which it can vibrate at high enough frequencies to generate its own metabolic heat—pretty darn impressive for an insect!

Like bumble bees, other native bee species do also have to survive the long, cold Canadian winters in diapause, but the bumble bee’s ability to stay warm sets it apart from other bee species when conditions are less favourable in the early spring and fall months. Bumble bees are capable of flying at much cooler temperatures (even around 10°C!) than most other insect pollinators, and this means that plants blooming at these times will also be pollinated. Sometimes even on cloudy days, very windy days, and during a light drizzle!

Our Ontario field crew might be all bundled up for spring surveys, but it doesn’t mean the bumble bee queens aren’t out foraging! Here is Aisa holding a yellow-banded bumble bee (B. terricola) queen she collected at Paddle-to-the-Sea Park, in Nipigon on May 17th when it was only 9°C! Photo © T. Harrison

3. They can buzz pollinate!

Bumble bees set themselves apart from many other native insect pollinators with their ability to perform what’s known as buzz pollination. Some native plant species, including Canada’s delicious native blueberries, trap pollen within their anthers that can only be released through small pores (imagine the holes of a salt shaker) when vibrated at a certain frequency. Bumble bees use buzz pollination to access these pollen resources! To do this, the bumble bee will grasp the flower with its legs, place its thorax close to the anthers of the flower, and will rapidly vibrate its flight muscles, producing a strong vibration that shakes the pollen free from inside the anther. Below, you can see a common eastern bumble bee (Bombus impatiens) foraging on rose using her special buzz pollination technique! (Note: turn up the volume so you can hear that wonderful buzz!)

4. They have long colony life cycles!

Of the insect pollinators we have in Canada, bumble bees are some of the earliest to emerge in the spring and are some of the last still out into the fall months. This means that bumble bees are critical players in the maintenance of important plant-pollinator interactions that many early and late-blooming plants depend on for reproduction. Outside of the warmest summer months, when insect pollinator diversity and abundance is usually at its highest, bumble bees are one of the most abundant insect pollinators! In the spring, take a closer look at some of the early-flowering willows, or at the goldenrod and asters in the fall – bumble bees will be some of the most common species you’re likely to see visiting these flowers!

Picture depicting the annual life cycle of a bumble bee colony. © Bumble Bees of Wisconsin – UW-Madison

We hope you’ve enjoyed learning more about what makes bumble bees some of the pollinators our Canadian landscapes depend most upon.  Don’t forget to keep your eye out for big, hairy bumble bee queens foraging on the few plants blooming early this spring, like willows and ephemeral spring wildflowers — they are always a welcomed sight in an otherwise quiet early spring landscape.

– The Bumble Bee Recovery Program