This is an identification from a newbie beekeeper. We think we've identified it correctly, but could of course be wrong. So we need a more expert opinion.
Below is a link to a you-tube video showing the Bombus Californicus on various flowers. One clip shows a 'cheater' bee sucking nectar from outside the flower...she stabs the nectary directly without having to go inside.
There is also a short clip of what we think is a Carpenter Bee.