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Do bumble bees hibernate or estivate?

Bumble bees queens hibernate. According to the Miriam-Webster site, hibernate means “to pass the winter in a torpid or resting state; especially : to pass the winter in a torpid condition in which the body temperature drops to a little above freezing and metabolic activity is reduced nearly to zero.”

Estivate, on the other hand, means “to pass the summer in a state of torpor.”

If you’ve ever watched a bumble bee, it is extremely active in summer and excess heat doesn’t seem to be an issue. In fact, most bees live in hotter and drier climates. Once a nest with workers is established, the bumble bee queen stays in the nest while the workers go out foraging. But the queen is not in a state of torpor, she is actively laying eggs and raising brood.

However, only bumble bee queens hibernate over winter, each one living separately in a small hole in the ground. The rest of the bees from her colony, the female workers and the males, die with the advent of freezing weather.

If you can’t tell a bumble bee from a honey bee, here is some help.

Rusty
HoneyBeeSuite

Comments

Glen Buschmann
Reply

While “hibernate” seems to be a good descriptive for bbee queens, at least one species common in our area, (western Washington) follows a summer torpor cycle. B. melanopygus, a large bbee with a boldly brick-red hind end, shows up with the crocus (late January to mid February) and disappears by the end of the Rhody season (mid-June). They use above-ground nest boxes, (such as bird houses stuffed with bedding), far more frequently than other species of bbees around here, and can be more territorial, (testy) around their nests than most. I’ve seen their nests overrun over by wax-moths at the end of the season; this may even be a reason these bees are a spring bee.

Glen B

Rusty
Reply

Glen,

I’ve tried to verify that, but I can’t. The forest service guide to western bumble bees shows Bombus melanopygus queens in King County, WA being quite active March through August, with a slight dip in May. I’ve checked with several university sites as well and find no reference to a summer torpor cycle for that species. If you let me know your reference, I will be happy to read it.

Glen Buschmann
Reply

A slow rereply. Our evidence is anecdotal, based on our observations. It may be that some B. melanopygus shows up higher elevation later, but around here (lowland Thurston County WA) they are definitely gone end of June, based on about 10 years of observation.

Glen Buschmann
Reply

One other note is that B. melanopygus are dependably out in February, sometimes even out in January. They emerge with crocus and disappear by the time rhododendrons finish blooming; they love rhodies.

Bill
Reply

Rusty,

I know I’m late to this conversation, but I’d like to make a small correction.

You said “However, only bumble bee queens hibernate over winter, each one living separately in a small hole in the ground. The rest of the bees from her colony, the female workers and the males, die with the advent of freezing weather.”

The slight correction is, it’s only the new queens of fall that emerged and mated that will try to winter over. The rest of the colony, including the old queen will perish before winter comes.

Rusty
Reply

Bill,

Good point. Poor wording on my part.

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