Found last week in an abandoned mine in Maramureș county, northern Romania. The light used is LED.
it can't be bugs because this was kilometers deep inside the mine, only fungi and bacteria here.
I tried asking on reddit but that was of no help (as usual)
What could the species be? Is it an undocumented species or perhaps undocumented behaviour? I couldn't find anything about it. I asked a few university profs. and they also don't knkw what it could be.
https://imgur.com/a/Eyu9dSJ