So I know you can get mites in there, and that it's not necessarily a big deal... but what about other bugs showing up?

Tonight my frog was going around hunting things I couldn't see again, so I started to REALLY look, and once I saw it eat a thin worm like thing off the fern (that one could have been a larvae since I have seen them act like that in the first vivarium where I got too many flies and they reproduced in there except that it seemed rather thin to be) But then I saw another white worm shaped thing that moved much too fast to be a larvae and more like a springtail.... could they show up without me putting them in there? Wouldn't that be ironic after my issues at getting a culture going?!