Stem borer (Diptera: Agromyzidae) in Agastache

The lower stems of the host are hollow except for an inner lining of pith. I found a puparium at the end of a tunnel in this pith layer in a lower stem, with the majority of the larva's tunneling having occurred at the base of the stem and apparently also in the plant crown and/or roots (although the belowground parts of the plant were not examined). Since I found the puparium intact in October, adults most likely emerge in spring. The posterior spiracular plates of the puparium bear upturned horns that are approximately half as long as the width of the plates.