Stem borer (Coleoptera: Erotylidae) in Nepeta

Larvae of this beetle that I found in winter 2022–2023 were dwelling in the lower senesced stems of catnip about 3-4cm above ground level, with one larva per stem. One larva I photographed was a pale yellow color. Each larva was accompanied in its stem tunnel by a small amount of frass, including, in at least one example, a frass plug. Additional larvae, which I located at another site in winter 2023-2024, had scraped away small patches of the pith layer lining the hollow stem interiors, resulting in irregularly-shaped gouges in the pith that were visible when the stems were cut open. At least one of these larvae turned out to be parasitized.

I reared adults from some of these overwintering larvae in spring 2023 and 2024. The color pattern of the reared adults is consistent with A. gracilis.