There are thousands of species of Collembola. I'm not sure what you mean by "mature" springtails,, but I would guess that you are seeing different species - bigger ones in your outdoor compost and tinier ones in your worm bin. There are probably tiny ones in the outside compost too, you just don't have a close-up a view of them there.

https://www.chaosofdelight.org/collembola/springtails/#all-about-collembola

Same question re. "mature". I see the tiny springtails in the 3 gal. bins but didn't notice in my larger bins or compost heap. Never put my nose that close, mind you.

Since they don't go outside the bins (I hope) and as long as they are not overpopulating the worms, I find that they break down paper products, especially CCB faster and that makes the VC real crumbly. Funny thing, I don't see them once the weather warmed up.

parsley: the link is very informative. Thank you. Where ever did you find these links? :‑)

Parsley, thanks for pointing that out. I hadn't considered that there could be so many different types of springtails. I think the white one in photos could be the one in my bins. I might check for the bioluminescence tonight. Those are some fascinating pictures. Thanks for sharing them!