The November before last I posted a picture of some wasp larvae a friend had found in the burrow of a wood-boring beetle larva while whittling by a campfire. The following May, I posted photos of the adult pteromalids. I suppose it was in the name of keeping things simple that I neglected to mention the beetle larva that was still living in the piece of wood.
On November 22, 2011, the same day I took the picture of the wasp larvae, I took this photo of a beetle larva’s face peeking out of a hole (about 1.5 mm wide) in the same piece of wood. If you look closely, you can see the grooves its mouthparts have etched in the floor of the tunnel.
For context, here is a photo I just took showing the above burrow at left and the cavity with the wasp larvae at right. I suppose I could whittle away the surface to see if they are connected, but it seems reasonable to suppose that this beetle species is the host for these wasps.
On May 15, 2012, the same day I took those photos of the adult wasps, the beetle larva had popped out of its burrow:
I tried to tuck it back into a hole in the wood, and it seemed to resume feeding:
The day I took those photos, I left for a week on Nantucket. When I came home on May 22, I saw that more wasps had emerged and that the larva had fallen out of the wood again but was still alive. Two days later I took this photo:
There is no note in my journal about this, but evidently I tried tucking the larva into the cavity where the wasp larvae had been, and then another adult wasp appeared from deep in the tunnel. On May 25 I wrote, “it appears that yesterday I successfully re-implanted the beetle larva in the red maple chunk, after more days of writhing on the bottom [of the container].” I checked the container throughout the year, and I’m sure I checked it this spring, but I don’t know exactly when was the last time I looked.
This week I’ve been going through all my vials, jars, and other containers, putting many in the fridge to overwinter and tossing some out. When I came to the container with this chunk of red maple, I found the 4-mm adult beetle inside, unfortunately deceased:
Since I had posted photos of the larva on BugGuide and had gotten feedback that it looked like a bostrichid (horned powder-post beetle) or possibly an anobiid (death-watch beetle), I browsed through the superfamily Bostrichoidea (in the process learning that things have been reshuffled and now Anobiidae is a subfamily of Ptinidae, which includes the spider beetles), and I believe it is the death-watch beetle Ptilinus ruficornis. To really appreciate those antennae, you need to see a live one, and Joyce Gross has been kind enough to let me use her photo here: