Hi April,
I've heard mention of these little critters before (sorry, I don't know their name), and I believe they are attracted to old wood on the vanda basket, if I'm not mistaken. If your vanda is in a wooden basket, these may be what you're seeing
You mentioned that the roots had some algae on them, so this tells me that the plant has been in a wet environment...the vanda loves this by the way. On the other hand, wooden baskets on vandas do break down in these conditions, and sometimes bugs will get into the rotting wood slats. If you've got other mounted plants of other plants in wood baskets, these (the mounts and baskets) can also be in danger of getting infested by your little visitors. If I saw them in my plants, I'd be sure to get rid of them, although I don't know what to recommend for you.