Stem borer (Lepidoptera: Noctuidae) in Ambrosia

I discovered a larva boring in a stem of the host in late July. I reared it on its original stem for about two weeks, then transferred it to a carrot. The adult emerged in mid-September.

In addition, I located affected stems in winter, after the stems had senesced and the culprit was long since absent. These stems each contained a large (~50mm long) spindle-shaped swelling near the base. Inside each swelling was a central cavity with some compacted frass on the upper and/or lower end, along with a large round exit hole opening to the stem exterior. One of the swellings contained a spent pupa in the central cavity with its anterior end facing the hole. The head capsule of the final instar larva was also present in the cavity along with the pupal exuviae. All the examined material appeared in close agreement with photos of Papaipema life stages identified as P. nebris in VanDyk (2024c) and Moth Photographers Group (2024), but I was unable to rule out the presence of more than one Papaipema species in my observations.