Bombus impatiens defensive behaviour
The photograph on the right shows the typical pose of a bumblebee who is not happy about something.
In this case it is probably the closeness of the camera, or it could be human breath (they don't like mammal breath), or both. The raising of one of the middle legs is always a sign to back off - the bumblebee won't sting, but it is disturbed by your presence.
Quite often if you back off and then move closer very slowly they will tolerate you. Also it is a good idea not to breathe too heavily, or to breathe to the side as mammal breath is not something they like. It is an instinctive thing as the only mammals that get this close are ones that are about to eat the bee or break into its nest.