Which brings us to the beetle.
Presence of the wasp is never good news for the wood-boring beetle Megacyllene robiniae. The wasp "parasitizes" the beetle's eggs, using them as depositories for its own eggs.
Indeed, the black wasp found by the researchers had a body "flat" enough to snoop around beneath tree bark in search of beetle eggs.
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Meanwhile, the beetle, no angel itself, is a rampant pest of the black locust tree (Robinia pseudoacacia): Its larvae bore holes in the tree's bark that are big enough to invite wind-blown fungus spores that cause rot in the trunk and branches of the tree from its center.
Fewer beetles, then, would be good news for the tree. Black locust trees, though native to the southeastern United States, are planted widely across the globe in temperate areas. In the eastern United States, it's a key honey source. The tree grows fast and its wood is tough and durable and makes great lumber, but the beetle's damage can depress that use of the tree.
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The Big However in all of this is that it's not yet clear how many of the lost wasp are out there. The researchers' chief goal was to re-establish the wasp and update its picture in the taxonomic photo album -- upgrading it to one with, for example, a head.
"We did it solely to redescribe the species taxonomically and make it recognizable, because the type specimens are incomplete and the original description was very poor and without illustrations," UCR entomologist and study co-author Serguei Triapitsyn told Discovery News in an email.
There's no way, Triapitsyn said, to know how many Oobius depressus are out there -- whether a small population or large -- without an extensive research survey.
But, with a new description on the way, identification of other specimens of the wasp will likely be easier. Perhaps they've been out there all along.
Detailed results of the UCR team's findings will be published in the journal The Great Lakes Entomologist.