While going through images after a session, there were a couple with a bumblebee’s middle leg raised up while another bumblebee was doing a flyby of the same flower (well, what’s left of the flower after a goldfinch had plucked all of the petals off!). Intrigued, a little research led me to bumblebee.org (highly recommended if you are into bumblebees), and it turns out bumblebees will raise a middle leg when they are feeling threatened as a form of defensive behavior. So now we know!