Perhaps you already know this but it was news to me: Cinnamon repels ants.
Cinnamon comes from the dried inner bark of a tropical evergreen, the cinnamon tree (Cinnamomum sp.). Ants would eat these trees alive if they could but the cinnamon genus evolved a very effective defense: two chemicals, Cinnamaldehyde and Cinnamyl alcohol, that are toxic to ants. Ants stay away from cinnamon.
In this 9-minute video, the guy from You Can Science It shows that even swarming, warring ants will drop what they’re doing when confronted with cinnamon. He theorizes that it changes their messaging from “Kill the other colony” to “Oh no! It’s cinnamon!” (video begins where he starts discussing cinnamon. Click here for the full video.)
Yes, cinnamon repels ants but it has to be fresh and you have to use a lot of it.
Read more about this experiment and the research behind it in this 2015 blog post at You Can Science It.
(photo and illustration from Wikimedia Commons, video from You Can Science It on YouTube)
Any difference between the real cinnamon (Ceylon) and the “false” cinnamon (Cassia)?
Both of them work, Rob — in the same genus. For the fine points of their differences see the reference links inside the You Can Science It article.