How much does it take to kill a bee?

Apparently a lot.. because we have bees in our wall that just won't go away.. Ron has sprayed enough bug spray to kill a horse but the danged bees just won't die.. he also sprayed expanding caulking in the hole where they were getting in but the old saying about bees being busy is true because they can get past the strongest deterrent known to man.. I have nightmares about the walls buzzing.. but tomorrow he's putting flashing all along the foundation so unless they have a blow torch or (what I'm afraid of) a back doorway into the basement.. we're good.. Plus it's too hot for my honey (pun intended) to be all decked out in beekeeper gear.