What Do Bumblebees Eat

What Do Bumblebees Eat?

Bumblebees are interesting creatures, not to mention important. They live in nests usually underground where the queen lays eggs and the workers forage and nurse. It’s not uncommon to wonder what bumblebees eat and that’s exactly what we’ll focus on today.

The Bumblebee’s Diet

As social insects, bumblebees live in a colony, ruled by a queen. Although bumblebees are always busy pollinating, tending to their offspring and queen, they still need food to survive, as all living beings do.

bumble bee ground nest

You may have guessed it, yes, a bumblebee’s diet consists mostly of nectar, pollen, and honey. These substances contain all the needed proteins and sugars to form a healthy diet for the bee.

Pollen

Pollen is what the bumblebees collect when out foraging on flowers. It’s not a liquid substance, rather it’s a very fine, smooth powder that male flowers produce.

The bumblebee collects a small amount of pollen and then carries it to another plant, usually female. She then disperses some of the pollen and thereby fertilizes the female plant. What the bumblebee didn’t leave on the flower, she will bring back to the nest.

Pollen is essential, especially for queen bumblebees. It’s rich in the proteins needed for her egg production. More on that further below.

Nectar

Nectar is a type of liquid, rich in sugar. Plants produce nectar inside glands known as nectaries. These sit either inside the flowers, where they attract pollinating animals and insects, or on the leaves or stem of the plant.

Nectar is very rich in sugar, and it’s also what the bees need to produce honey. The bumblebee inserts her long tongue into the flower to reach the liquid.

If she can’t reach the nectar this way, she will use her mouth to bite a hole in the flower and suck out the nectar, which she then stores in her stomach. Nectar is important for a bumblebee’s diet since it provides them with energy and water.

Honey

We’re all well aware that honeybees produce honey. Bumblebees, on the other hand, also produce honey, or at least, a close lookalike. Bumblebees don’t make honey as we know it, instead, they store the gathered nectar in nectar cups.

bumblebee nest

Honeybees make their honey by mixing nectar with an enzyme in their stomach. They then place it in the hexagonal cells where the other bees flap their wings to evaporate the water. Bumblebees skip some of those steps and just place the mixture in the nectar cups.

Honeybees produce and store massive amounts of honey so they have enough to survive the winter. Bumblebees, however, only produce and store what they need for now. They never store up as much “honey” as honeybees do, because most of them don’t live through the winter.

Honey, nonetheless, is an important part of the bumblebee’s diet. Much like nectar, it provides energy for the queen and larvae.

Diet of the Bumblebee Queen

The bumblebee queen is the most important member of the nest—she’s the founder and mother of all the colony. A bumblebee colony only survives until early to late autumn, where the queen will produce new queens and drones.

Before winter comes around, the new virgin queens emerge from their nest, ready to mate with a nearby drone. After she’s impregnated, the new queen needs to fill up her body with pollen and nectar so she’s ready for hibernation.

ground bees

The bumblebee queen will snooze for as long as nine months. She finds a place underground and gets comfortable. As you can imagine, going such a long time without food has a significant impact on her energy stores.

When spring warms up the earth, the queen wakes up. She is completely drained of energy and her body temperature needs to be at 86 degrees Fahrenheit before she can fly. So she sets out on foot to find nectar. Because of the high sugar content in nectar, it won’t take long for the queen to have enough energy to finally take off.

bumble bees inside some wood
CC Image courtesy of allan_harris

To get her ovaries working, she’ll also need pollen, which is an essential source of protein. Pollen contains specific chemical compounds, that help activate the queen’s ovaries. Without pollen, she can’t lay her eggs.

Once she’s fed, found a nesting spot, and lays her first batch of eggs, she’ll make a small wax pot. This is where she’ll store nectar, which she will eat while incubating her eggs.

Over the course of her lifetime, the queen will mostly feed on pollen. She may also mix in some nectar occasionally, to keep her energy levels up.

Diet of Bumblebee Workers

Bumblebee workers have quite the opposite diet to their queen. While the queen focuses her diet on protein, the workers, especially foragers, need more energy. These will feed primarily on nectar to fuel their heavy bodies for the long foraging trips.

The foragers will actually fill up their stomach with nectar before flying out of the nest. This gives them enough energy to reach the flowers and back again to their home, they would die of exhaustion otherwise.

The larvae, still in their cells, will feed on pollen provided by the queen. As they develop, they’ll eat more nectar and pollen, now fed by the other grown workers.

One interesting fact, however, is that before they emerge as fully evolved adults, they have to feed on their sisters’ feces. Yes, bumblebees eat poop.

No, this is not a silly test they have to pass in order to be accepted in the nest. The feces will actually protect their stomachs from deadly parasites. Inside their sisters’ feces are helpful bacteria that strengthen the newly evolved bee’s immune system. We may know them as “gut bacteria” and it’s something nearly all creatures have.

Humans have over 100 trillion microbes that help us digest food, filtering out the bad by outnumbering potential disease-carrying bacteria. It’s the same for the bees—so although it may sound repulsive, it’s crucial for bumblebees.

Diet of Drones

Male bumblebees, or drones, usually emerge right before the new queens. Drones will only stay in the nest a couple of days at the most, before they venture out to mate.

bumble bee nest
CC Image courtesy of orangeaurochs

While still in the nest, they’ll feed on honey and pollen to build up enough energy to fly and build up their sperm supply. Once out in the wild, they’ll usually find a queen, mate and die.

The drones that didn’t manage to find a queen may feed on either pollen or nectar on flowers. They rarely return to the nest, even at night. Instead, males may sleep under flowers or other hidden places.

Summary

Bumblebees are very interesting and quite different to honeybees or other species of bee, but their diet is not so dissimilar to that of other bees. They feed mostly on nectar, pollen, and homemade honey—but the new adults also feed on fecal matter, to strengthen their immune system.

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