Rosy Knot-horn Oncocera semirubella

This species was previously assigned the vernacular name Rosy-striped Knot-horn which I think is actually more appropriate. It's also sometimes known informally as Rhubarb and Custard, though that should really be Custard, Rhubarb and Cream.

This species is increasing in Norfolk and appears to be breeding in the Brecks and probably elsewhere (e.g. Flitcham). It was a species I was longing to find, so was delighted when one appeared on the top of my moth trap while I was going through it one morning. It must have made its way out of the trap while I wasn't looking as it hadn't been there earlier. I took a single photo and looked back only to see that it had vanished. Afraid that the flash had flushed it and I'd missed the shot I checked my camera and was relieved to see that I had got it. I didn't see it again, so good job it's a very easy species to identify!

Rosy Knot-horn Oncocera semirubella, North Elmham (Norfolk, UK), 17th July 2025

I didn't have to wait long before another one turned up. This was more obliging in terms of sticking around for me to take photos but being a much more worn individual it wasn't half as pretty as the first one.

Rosy Knot-horn Oncocera semirubella, North Elmham (Norfolk, UK), 25th July 2025

Rosy Knot-horn Oncocera semirubella, Cooper Street, near Ash (Kent, UK), 16th July 2026

Rosy Knot-horn Oncocera semirubella, Cooper Street, near Ash (Kent, UK), 17th July 2026

I'm not sure if I'd have realised what this was so quickly had I not seen a photo of a very similar example recently. At some angles some pink was visible but at other angles it seemed more-or-less uniformly buff.

Rosy Knot-horn Oncocera semirubella, Wendling Beck Project (Norfolk, UK), 12th August 2026

I assume these are now breeding more widely across Norfolk, including not too far from my neighbourhood.

Rosy Knot-horn Oncocera semirubella, North Elmham (Norfolk, UK), 13th August 2026

I'm pretty sure from the position of wear that this one is the same as the one above, retrapped the following night.

same Rosy Knot-horn Oncocera semirubella, North Elmham (Norfolk, UK), 14th August 2026