Help identifying pest

[T0dd]

Hello, I am very new to orchid growing. I tried a couple several years ago, promptly failed, and gave up. More recently I decided to give it another go. I bought a small light for them, and things have been going well. I have several small plants: Dendrobium, Masdevallia and Epidendrum.

In the last couple of weeks I seem to have developed a pest problem, and I'm hoping someone can help me identify and treat them. I've posted the best photo I can get, but it's not easy, as these things are tiny.

After watching these things for several minutes, I'm nearly convinced they are not mites, as I am 99% sure they only have six legs, and are thus insects. They don't have any wings that I can see, and I haven't seen them jump or fly. Their bodies are very bulbous, and from a top view appear to be essentially spherical. They look very much like small ants with the middle section (thorax) chopped out.

The one in the photo is the largest size I see and you could fit several of these on the head of a standard pin. There are many that are smaller, as small as maybe one-fourth this size, and there are also some VERY tiny nymph/larvae that are translucent. So far I don't see any on the orchids at all; they seem to be crawling on, and eating, the sphagnum.

I'm in the midwest, and am growing these entirely indoors, if that helps. Hoping someone can tell me what these are! If not, should I just treat with some broad spectrum insecticide? And if that's the recommendation, some basic info about how to do this would be very helpful, as I've never done this before. I don't know if I should mist with insecticide, or remove the plants and root systems entirely from the substrate, and soak, or what.

Any advice at all would be immensely appreciated. Thanks!