PS: species ID confirmed by Frans Janssens via BugGuide:
https://bugguide.net/node/view/1912378#3153111

I found an upside-down bolete (type of mushroom) during a dog-walk in the woods, picked it up, and turned it over. When I spotted the group of critters, the thought of springtails never entered my head; they were too big! I started taking photos thinking, maybe barklice or something? But then I saw in my photos that they were definitely colossal collembolans. Note the much more typically-sized springtail (i.e. so tiny that I didn't even see it when I took the photo, as is the case with several of my springtail pics) in the upper left-hand corner of one of these photos. For some further context as to size, note my thumb in the lower left-hand corner of another. These beasts are nearly as long (counting antennae) as my thumb is wide! Hopefully I'm placing the big ones in the correct species here.