Any chance of a photo? Nothing I've seen is coming to mind that would arrive as a group - several in the same plant.

Are they doing damage, or just there?

Camara not working, maybe I can use my daughter's. Dozens in the same plant x multiple plants around a big yard. They are eating the plants.

I found something called coreopsis beetle using google, but it is more yellow and black striped with red near the head. Take a look and see if that is it : Calligrapha californica and Acalymma vittatum are two that are mentioned and there is another one that looks sort of like a ladybug. Not sure what you can do except choose something to spray them with.

ramazz, nice tip. I find mention of them in OSU ipm garden management, but haven't seen them and I have lots of thread leaf coreopsis, many years planted.

Here is a link that might be useful: Clc70, Like this?

It is such a "buggy" year!!!! I don't have a clue about the beetle but I wanted to empathize as I have more eaten up seedlings than ever before. Sunday I planted out good sized seedlings of a perennial lobelia (a dark purple one I found last year among my Lob. sip light blue ones and saved the seed) and today they are in tatters - don't think they are going to make it.

Even working in the garden is harder with all the flying bugs. I use to get bothered as it got closer to sundown and they started hyping up, but there are so many I feel like I am being nibbeled at all day long.Drives me nuts. I guess I am going to have to start putting spray on myself.

I hope the beetle leaves you some flowers.....

I wonder if it may be the same beetles that infested my Pot Marigolds (Calendula) last year? If I remember correctly they were called Blister Beetles. They never caused no harm, and were mostly seen on or very near the bright yellow and orange flowers. I never did see them on my Coreopsis lanceolata though....just on the Calendula....hmmm
I know yours are stripped and mine were solid black, but these beetles are more than one species.

Here is a link that might be useful: Texas A&M Etomology Dept

I wonder if it may be the same beetles that infested my Pot Marigolds (Calendula) last year? If I remember correctly they were called Blister Beetles. They never caused no harm, and were mostly seen on or very near the bright yellow and orange flowers. I never did see them on my Coreopsis lanceolata though....just on the Calendula....hmmm
I know yours are stripped and mine were solid black, but these beetles are more than one species.

Here is a link that might be useful: Texas A&M Etomology Dept