I was out in my garden when I heard a be's buzz. Looking round I saw a small non-bumble, non-honey bee -- my best assessment it is was one of these (image) (https://www.wildlifetrusts.org/sites/default/files/styles/scaled_12_col_desk/public/2019-01/male%20feather%20footed%20flower%20bee%20anthophora%20plumipes%2012-04-2015%2013-56-010.JPG?itok=ohU3fLUI) Feather Footed flower bees (info) (https://www.wildlifetrusts.org/wildlife-explorer/invertebrates/bees-and-wasps/hairy-footed-flower-bee).
It was on the ground, on its back spinning its wings like crazy whilst doubled over apparently grasping or biting at its own abdomen. I looked from as close as I dare -- a few inches away -- and I could not see anything -- ants, mites -- that might be the cause.
I then ran inside to get my camera, but by the time I returned I could not longer find it.
Any thoughts about what might be(e) the cause?
Behavior like that is almost certainly not normal. Perhaps the bee was attempting to aggressively clean some harmful substance off itself, perhaps something was preventing it from flying normally and it was trying to right itself, perhaps it had been exposed to a neurotoxin of some sort and just wasn't thinking properly anymore. Hopefully the fact that you couldn't find it when you came back means it was all right enough to fly away.
Just this afternoon I was out eating lunch at a park with my family, and I found a carpenter bee female who was struggling on the ground. She was missing one antenna and was acting very defensive, so I got her onto a stick and moved her out of the walkway. It's a rough world out there for bees.
There are at least 751 kinds of mites that live on bees. Some live on honey bees and other bees as well. The mites vary in size from microscopic to large enough to see. My guess would be a mite.