Back in August I gave a talk and co-led a walk at an event in southern Ohio called “On the Trail of E. Lucy Braun”, a celebration of the life and work of a renowned Ohio botanist and conservationist. I was there, of course, to make sure Lucy’s sister Annette was properly represented. The walk took place at Lynx Prairie, a site the Braun sisters visited regularly. On August 25, while we were scouting for the walk, Julia spotted a single mine of a Brachys larva (Buprestidae) in a leaf of hophornbeam (Betulaceae: Ostrya virginiana).
This beetle genus is primarily associated with oaks, apart from the recently described Brachys howdeni on trailing arbutus (Ericaceae: Epigaea repens). Any larvae found on other host plants are of particular interest as Henry Hespenheide works to revise this confusing genus, and hophornbeam was a new host record as far as I knew. So I kept a close watch on this larva after we collected it, struggling to decide whether it was better to preserve it for DNA barcoding or attempt to rear it to an adult (which was by no means guaranteed to succeed, and would involve waiting until spring).
On September 1, I was dismayed to discover an ectoparasitoid attached to the larva:
So the decision was made for me. As we saw in my previous post, I didn’t have much time to lose before there was nothing left of the larva. I tore open the mine, giving me a better view of a parasitoid larva than I normally get to see…
…and then I wrested the parasitoid away from what was left of the beetle larva, plunking the latter in a vial of ethanol so I could try and get a DNA barcode from it later. I offered the wasp larva a Brachys larva from another host plant, but it showed no interest in it. Instead it wandered the rearing vial forlornly for several days, finally settling down to pupate on September 5. My pictures of the pupa aren’t great because the first was taken through the wall of the vial, and the second was taken at an awkward angle looking down into the vial.
As you can see, this larva deposited liquid meconium rather than the apparently solid pile left by the Stigmella parasitoid. Between ten and twelve days later, the adult emerged (while I was away at the Berkshire BioBlitz, so I didn’t get to see it alive).
I suspect she’s another Pnigalio (Eulophidae) of some sort, but time will tell.