These show up every year and skeletonalize my hardy hibiscus every year until I get fed up and end up spraying them. I could put up with them if there weren't thousands of them! Are they sawfly larvae?
I don't know what they are, but my herbaceous hibiscus get them too. They seem to appear in swarms and chew up the leaves almost overnight. If I'm lucky enough to catch them when they first hatch a spray with insecticidal soap will usually wipe them out.
kill them lol, they are ugly and not good moths. I think it is a Rose of Sharon Moth- Anomis commoda. Only 3 others feed on hibiscus Yellow Scallop Moth- Anomis erosia, Glossy Black Idia- Idia lubricalis, and Io Moth- Automeris io. Io moth is a pretty moth but the cat will sting the fire out of you