An online resource based on the award-winning nature guide

Flight of the Bumblebee

bumblebee and turtlehead 049A4838If you examine plants that are still flowering this late in the season (such as asters, goldenrod and late-blooming turtlehead) early in the morning when it’s still quite cool or late in the day, many of the pollinators you see will be bumblebees, not honey bees. One reason for this is that they have different temperature tolerances for flight. You rarely see a honey bee when the temperature is below 57°F as they cannot fly when it is this cool. Bumblebees, however, are capable of flight when the air temperature is as low as 50°F.

Even so, bumblebees cannot take off unless their flight muscles are above 86°F; they maintain the temperature of their thorax (where wings and wing muscles are located) between 86°F and 104°F regardless of the ambient temperature. The way in which they raise the temperature of their thorax involves uncoupling their wing muscles so that the wings themselves do not move. They then use their wing muscles to shiver and raise the temperature of their thorax until it’s sufficiently warm enough for them to fly.

At rest a bumblebee’s body temperature will fall to that of its surroundings. If it is cool out, and the bumblebee wants to take flight, you can actually see its abdomen pumping to ventilate the flight muscles. An entomologist studying this phenomenon discovered that the rate of pumping can give an indication of the temperature of the bee. It ranges from around 1 pump per second when the bee is 86°F, to 6 pumps per second when it reaches 95°F.

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6 responses

  1. How do I love thee, bumble bee? Let me count the ways…. 🙂

    September 13, 2017 at 7:58 am

  2. Alice Pratt

    So much info! I plant & let wild things grow for pollinators….it’s amazing to see how busy they are. From early Spring till the last flowers die, there is a multitude of flowers available for them in my yard.

    September 13, 2017 at 8:59 am

  3. Kathryn

    Are we seeing as much bumblebee decline here as other areas are? I seem to still be seeing quite a few. Long live the bumblebee…

    September 13, 2017 at 9:43 am

  4. Fascinating, Mary!
    As an aside, Japanese knotweed has taken over the riverbanks below us and their flowers are buzzing with literally hundreds of honeybees. The air vibrates…it’s astonishing. Two non-natives, in love. 😉

    September 13, 2017 at 8:43 pm

  5. judilindsey

    Mary,

    Simply fascinating – as always!

    Judi 🙂

    >

    September 14, 2017 at 6:17 am

  6. Guy Stoye

    When beekeeping in the sixties on Long Island, I used to have my bees sometimes coming out on milder, sunny winter days for “exercise flights” which appeared to be not longer than a few minutes.
    They would travel circular around their hives and after one of these sessions there were thousands of tiny, brown spots on the snow. I don’t know what the air temperature was- perhaps 60 or above but I think not.
    Haven’t seen one honey bee around our neighborhood in Danbury, N.H. this year nor but two bats in our two large bat houses. Worrisome.
    Nice posting about the bumblebees. How we love them. They even tolerate having their backsides gently rubbed while they’re working on the flowers.

    September 14, 2017 at 3:02 pm

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