Antlion, dead in a web amidst debris.
Lots of antlion pits, beneath a wooden structure that was like a table-bench with a roof. People often tended to hang out there (and in similar structures), hence the buildup of trash beneath.
An observation of an individual antlion is https://www.inaturalist.org/observations/2618051
Antlion larva in its pit, and then removed for easy viewing. (It is probably not visible in the first picture, being covered in pebbles; I had to dig it out a little.)
Here is a video of it building its pit: https://www.youtube.com/watch?v=fXAiEh6JopI
An observation for lots of other antlion pits in the same area is https://www.inaturalist.org/observations/2618079
I don't know if these images are sufficient to take this ID down below family level, but if anyone has a suggestion, please comment. Ph. at a porchlight in open juniper-oak woodland.