YA Fantasy teenagers. VERY specific detail I remember: Main characters discover a migration of Beetles walking in Line with blue or red on their back. Read before 2017.

[Colline]

Hello dear reader,

Currently trying to list the Books I have read in my life, I often have some memories coming back but impossible to remember the whole story and name. Can you help me with those details? :
- Type : Fantasy novel,
- Audience: Probably teenagers.
- Year: at least 9 years ago (2016), probably more (2012-2015). So not more recent than this.
- Main caracters ' type : humans
- Story details:
I remember that at one point in their adventures, the main character (or characters) discover a line of beetles walking outside. They are in a line, migrating in one direction. They have a specific color or symbol on their backs. The characters wonder where they are going, whether it is a magnetic pole that attracts them, for example, I don't remember.
Following this passage, they find themselves in a large forest. There, they discover a village perched in very tall trees.

Good Luck with this and thank you!!

[Colline]

Sorry, Beetles, not Beatles 🤣🤣