ID tentative.
Found on some kind of red oak (245682974).
If the ID is correct, it's really strange. Having never seen one before, now I've seen 3! And all on oaks (although not the same species).
Hymenoptera (Ants, Bees, Wasps and Sawflies) » "Parasitica" - Parasitoid Wasps » Trigonaloidea » Trigonalidae » Taeniogonalos » Taeniogonalos gundlachii