Why ants gathering on terrarium lid.

[Saga pedo]

Hi, does anyone know why my ants (Camponotus vagus) are gathering in a small group on the lid of their terrarium?
They have water and food and are just awakening from hibernation, barely exploring their fishbowl arena.
When I disturb them they all rush back into their nest, but otherwise they sit motionless right next to each other. It is a small colony, approximately 100 ants with plenty of space to expand .
I'd like to hear your thoughts about what could cause this abnormal behavior

In the Photo i axidentaly disturbed them so most left.

 

[Brewser]

Scouts ... ...

 

[BoyFromLA]

To plan to escape, to take over the world.

 

[Saga pedo]

You know, I just read a book about this subject.
I think i have to upgrade my seurity systems!

 

[WhiteMoss]

If they're coming out of hibernation, then that's likely the warmest spot of their set up. Just trying to absorb some heat most likely.