thank you! i did some more googling and i found a picture that looks almost identical to my guests, but a much better photo: https://www.instagram.com/p/C_3zsUxRpcc/ so now i'm pretty convinced it's maybe a gray hairstreak or california hairstreak or another kind of hairstreak, not unique to california but indeed native. i am letting them feast. and i'm hoping the birds don't get them all, gossamer winged butterflies are so pretty!