Subject: Unknown hymenopteran
Geographic location of the bug: south eastern PA
Time: 04:35 PM EDT
Your letter to the bugman: Hello. I am the plant protection intern at Morris Arboretum of the University of Pennsylvania and our arborist saw this insect fly out of a diseased Juniper. Can you please help me to ID it? I am sorry that he removed the insect’s head. I took this video because it is still moving.
How you want your letter signed: Jenny
Because of the coloration, what appears to be a long ovipositor at the tip of the abdomen, and the written description that it emerged from a diseased juniper, we believe this is a Braconid, a parasitoid Hymenopteran in the family Braconidae, which is well represented on BugGuide. We have an old posting of Braconids swarming on a grape trunk in California, and at that time, Eric Eaton noted “so few braconids are parasitic on wood borers.” We also have this UK sighting in our archives that we believe to be in the genus Atanycolus. That genus is represented on BugGuide where it states: “Parasites of woodboring beetle larvae, especially metallic wood-boring beetles (Buprestidae) and longhorn beetles (Cerambycidae).” Since your juniper is diseased, it is probably infested with wood boring beetle larvae, the natural prey for parasitoid Braconids in the genus Atanycolus, so your arborist seems to have decapitated a beneficial predator and part of the solution, and not the cause of the problem for the tree, which is why we will be tagging the posting as Unnecessary Carnage. If the tree does have a bad infestation of borer grubs, you might see additional Braconids emerge. The female Braconid uses her ovipositor to deposit eggs beneath the bark of an infested tree or other woody plant, and the hatched larvae feed on the larvae of the beetles. Adults emerge after pupation, so it is an understandable mistake to believe the Braconid is a harmful insect when it emerges from the tree. We hope the information we provided will score you a few extra intern points.
We were able to get a better still from the video to illustrate the posting.