They're most likely springtails.
https://insects.tamu.edu/fieldguide/aimg1.html
Springtails are harmless.
But...
Springtails in your potting media means there is vegetation rotting. That's part of their diet - dead plant material. They don't cause the death of the roots, they feed on what's already dead.
If there isn't a whole lot of rotting vegetative material, and the potting media is dry, they won't be present in noticeable numbers.
They live in dark and moist places because that's usually the same type of environment that causes rot for some plants.
If you or your friends have thumbnail dart frogs, thumbnail dart frogs love these guys. They eat them like candy!
---------- Post added at 09:27 AM ---------- Previous post was at 08:50 AM ----------
In terms of your orchids, it is probably time to repot into fresh media and check the health of your orchids' roots.
---------- Post added at 09:28 AM ---------- Previous post was at 09:27 AM ----------
Btw, use a jeweler's loupe and take a photo of the enlarged image in the lens of the jeweler's loupe.
Someone who posted about this same problem did what I described.
Here's a link to thread with the set of photos he posted. The one you want to pay attention to is the 1st pic on the bottom row in the very first post:
http://www.orchidboard.com/community...aves-fast.html