Notice how small they are.  The perlite is your standard size, and it looks like boulders next to these guys.  No wonder they can go undetected for so long. You need to look with a magnifying glass.  I also get white springtails which are about the same size.  The difference is that the springtails wiggle.

Notice how healthy the plant they came from appears.  It had been blooming well and no yellowed leaves. 

I had already removed four bottom leaves for propagation when I took the photo.  I then washed off all the soil from the roots.  Then I soaked the root ball in Sevin.  It's doing fine on it's own reservoir again.  I'll watch this one for years, before I consider it 'clean'. 

Remember to inspect the root ball thoroughly.  Even after 20 years, I still get fooled!