Thanks, iddee. I know I have seen bumble bees sleeping 'on the job'. I watched a bumble bee crawl and work her way deep down into a blossom. After she got in as far as she could she became very still. I assumed she was sleeping.
Also, I heard Tom Seeley give a presentation on in-hive activity. He played audio sounds he had recorded. Tom explained that some bees will go around waking other bees by head butting them and making a "beep" sound. Seeley said that meant "Wake Up, Let's Go!" So, I assumed they slept, but didn't have a good quote like iddee.