Kinda hard for me to tell from the pic if a millipede or centipede. A centipede has one set of legs per body segment and antennae. Millipede has 2 pair of legs per body segment and no antennae. Pretty easy to tell apart. Pic kinda looks like a millipede.
Centipedes eat other bugs so ok to have around outdoor grows. Wouldn't want them in my indoor grow or greenhouse. Won't bother the plants though. Some a have poisonous bite!
Millipedes prefer to eat decaying plant matter and will eat decaying animal matter if no plant matter around. They like it dark and damp. If it gets too dry for them then they will eat wetter things like cannabis roots! If dry enough they will eat cannabis leaves! While they generally cause no harm, why take a chance, get rid of them.
A friend makes compost for his vegetable garden. I use this compost for part of my soil mix. It is loaded with centipedes and millipedes. I get rid of them all as the plants are started in my house.
I make my own compost, so I guess it makes sense. I wonder If the hot temperatures drove them to surface. Anyway, I sprinkled some
Diatomaceous earth on top of the soil. Plants look ok. I’ll post back if anything changes