If I just pull the top layer of castings away there are little soil mites; no idea what the difference between them and a springtail is but these guys are jumpy. I'll take video next time I pull castings from my worm factory.
I keep recycling my soil but do not notice them after a harvest so they must die off..I mean where would they go if they just leave to look for new cunts to munch on! Lol dead bugs are consumed by fungus in your soil which btw also eat dead worms yum- good nutrition for your plants. Don't worry your weed shouldn't taste like bugs or dead worms unless of course you smoke the roots.
The difference between a springtail and a mite is vast but ultimatly its main difference to a mite is that it has a appendage under its body that when released allows it to jump into the air, a mite has no jumping capabilities and hence how you can tell them apart in soil.
A sprintail will eat your soil not the roots and why it lives there, its ability to jump is a defence mechanism allowing it to flee predators and hence if you disturb them they jump around like crazy.
Often you wont notice springtails till you water and they need to come to the surface for air. They are totally harmless and dont affect the plant or worms and i generalise about the soil springtail as they are very diverse and have colonized most habitats including the lakes and oceans.
Im almost willing to bet that you have springtails as no other soil bugs show the description youve given and although most might not have heard of them i assure you it is quite common on rollitup and a quick search for 'springtails rollitup' will shot you up a load of threads on them and maybe even one or two ive written on the subject over the years as i too have had them once or twice.
Im a gambling man and can deal with the shame of being wrong so im going to challenge you and say im 100% sure youve got springtails dude, prove me wrong