Stem borer (Coleoptera: Erotylidae) in Monarda

Tunnels in stems of the host. Because stems of the host are at least partially hollow, much of the larva's feeding involves excavating the layer of pith lining the inner walls of the stem. Two larvae collected from late June to mid-July emerged as adults at the end of July. Both larvae were yellowish in color, not orange like most larvae of a more common species of lizard beetle (Acropteroxys gracilis) encountered in the current study; the pupa was also yellow. Additionally, I located a deceased adult in a tunneled stem of the host in winter, after the stem had long since senesced. The adults all appeared externally similar to Languria trifasciata, based on images of that species at BugGuide.net (VanDyk 2024d).

Additionally, I hypothesize that an egg I found in the stem of a spring shoot belonged to this species, based on similarities with erotylid oviposition observed in an unrelated host (J. van der Linden, unpublished data; also note Tangren and Frye 2020). I've included the egg record, though uncertain, on this page in the images below for the sake of completeness. Given the fact that L. trifasciata has been reported from the Northeast and Midwest at least as early as mid- to late April (Carr and Alexander 2013, Moorehouse and Hedlund 2022), it does not seem unreasonable to suppose that at least some adults could lay eggs in spring shoots of their host plants.

L. trifasciata has been previously reported as a stem borer in Lactuca canadensis (Chittenden 1904).