I can’t offer any taxonomic erudition today — I have no idea what species of bumblebee this might be, or even what kind of flower it’s pollinating — but the bees sure do make a cool sound.

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There’s a higher-pitched buzzing, more mosquito-like, along with the normal sound of buzzing bee wings.  It turns out this is something called “buzz pollination,” where the bee grabs the flower and vibrates the hell out of it, releasing pollen that would otherwise stay in place during a casual pollination visit.  It’s a symbiotic evolutionary arrangement whereby the flower gets to hang on to its pollen (energetically expensive to make) except when the right pollinator is visiting, and the bumblebee gets access to a semi-exclusive resource.

Update:  A couple of friends pointed out that this flower is in the genus Chelone, with the species probably obliqua.  The common name is turtle head.  Thanks to Denise Leonard and Roger and Ann Sweet!