The parasitic wood wasps, family Orussidae, are closely related to sawflies and horntails. They are rarely seen and quite striking with their cylindrical shape, round head, and antennae that sit low on the face below their eyes. Their larvae are ectoparasites (live on the outside of its host) of woodboring larvae, usually metallic woodborers (family Buprestidae). The females, recognized by their swollen antennae tips, will use echolocation to locate hosts along dry, bark free wood. As they run along logs, they tap the log surface with their antennae. These vibrations in the wood caused by the antenna taps are perceived by the forelegs, helping them hone in on suitable places to lay eggs. Males also tap their antennae as they run along logs.
Photo by Heather McKee on 7/17/20 near Missoula, MT