Something laid eggs into the tree above the chair. They hatched into larvae and fell onto the chair. Butterflies and wood boring beetles use trees to lay eggs, but a fairly large number of insects can also do that. Google has an app for that, but you may need to have a closeup, the resolution of this image is not sufficient.
You may want to look into the tree, it might have some eggs that have yet to hatch.
@Northwest No. they came out of the wooden pergola above the deck. The are actually carpenter bee larvae. It was 108 degrees yesterday. Perhaps that’s why they fell out of the nest above.
@CereBellum The heat may have nothing to do with it. They could simply have fallen off. I often find larvae falling from the trees down to the deck. If the source is the wooden pergola, you may have bigger problems, as in your wooden pergola needs to be treated. I had my pergolas insect-treated, prior to construction. Larvae still falls down from the grape vines.
