A patch in my garden is suddenly covered by hundreds of tiny crawling critters. They are light brown or tan, and range in size from smaller then a pinhead to a bit larger then a pinhead; they have six legs, small antenna, and no visible wings. I scooped up a handful of mulch and put them and the substrate in a jar, and took a video through a magnifying glass. A link to the video is at the bottom of the email; it is pretty fuzzy. I'm wondering what they are, and if there is any connection to nearby plants suddenly shriveling up.
Fungus Gnats? They lay eggs in the soil and the larvae hatch there, eventually metamorphising into tiny little flies that are really annoying. The larvae can damage plant roots.
I get them in potted plants in the house, and usually deal with them by putting a layer of sand or small gravel on the soil- if the gnats can't get to the soil to lay eggs the population declines. I'm not sure what I would do in an outdoor garden situation, diatomic earth might help.
I have to admit that I didn't watch the video, but your description sounds exactly like some critters that showed up in my worm bin while I was having major fungus gnat issues... fungus gnats are now rare, and if I have fungus gnats in any of my houseplants, they get some vermicompost, no more gnats. This leads me to believe that they might be hypoasis miles. Good guys. I would suggest checking some of the roots for root aphids. These predator mites could be thriving because they have lots of pest to eat.
And thank you for asking a question that finally motivated to register.
No wings; and yes, very fast. I took another look through a magnifying glass. They have fat, pear-shaped abdomens, six legs, fairly long antenna (as long as their legs), and a small thorax. There is a range of sizes, with the smallest almost half the size of the largest. And they are moving constantly.
I watched the video and got the 'impression' of a nymph stage of a squash bug/stink bug. They hatch out in a large group and then run around a lot. They can cause squash leaves to wilt even early in the season. Seems early for them though, I haven't even planted squash yet.....and I don't think I've seen them that small.....
"We're all just walking each other home." -Ram Dass
"Be a lamp, or a lifeboat, or a ladder."-Rumi
There is getting to be more and more of these critters on the soil surface.
However, I have a thought. The critters in the jar are still alive. There are no green growing plants in the jar with them. Does that mean they are living on soil organic matter, and therefore benign? Or could herbivore insects live that long without food? Or could they eat both, like pillbugs do? Or could more and more be hatching out of the mulch in the jar, replacing those that die?