I noticed ants crawling all over and inside two of my hives today, so I surrounded the hives with cinnamon.I’ve read many times that cinnamon repels ants, though I’ve never seen it myself. I sprinkled some cinnamon around one of my hives a year or two ago, but then it rained, so I don’t know if it works. Whether it works or not, I’m not too concerned about the ants. I think it would take a biblical amount of ants to do significant damage to a hive full of bees. We’ll see.
July 2019 Postscript: Maybe the cinnamon repels ants. Maybe it doesn’t. I guess there’s no harm in trying it out of desperation, but these days I don’t bother. The ants will be around for a little and they usually disappear and never really cause much trouble.