A few weeks ago I collected some burdock seedhead hibernacula, constructed by the moth Metzneria lappella, that had been raided by one or more tufted titmice (and possibly other foraging birds). The birds had pecked irregular holes in the hibernacula to get at the moth larvae inside, and I wanted to photograph the damage. Some of the holes pecked in the hibernacula seemed too small to allow passage of the moth larvae, which are quite large and fat. I wondered if these hibernacula had been parasitized and the birds had pecked them open just enough to discover this. Sure enough, one of the first raided hibernacula I tore into harbored this adult wasp, which presumably had metamorphosed in the few weeks since I'd collected the hibernacula and brought them indoors. (Another raided hibernacula held at least 2 wasp pupae/puparia). Numerous similar-looking wasps emerged from intact hibernacula I collected for rearing in 2015 (see below), so I assume this is a parasitoid of the moth.
This being a very small and lively specimen, it was difficult to get sharp photos, so I apologize for that; please feel free to frass any images that won't help with ID.
I think it's way cool that this wasp has grooves in its head into which its antennae can be folded!
Similar-looking parasitoids I reared from burdock hibernacula in 2015: