The wasp, Agenioideus nigricornis, was first described by entomologists in 1775 but has had little scientific attention in the intervening centuries.
"Since then, scientists have largely forgotten about the wasp," biologist Andy Austin at the University of Adelaide said. "It is widespread across Australia and can be found in a number of collections, but until now we haven't known the importance of this particular species."
The importance is that the tiny wasp has been shown to be an effective predator of the Australian redback spider, a relative of North America's black widow spider.
"The redback spider is notorious in Australia, and it has spread to some other countries, notably Japan and New Zealand," Austin said.
"Redbacks are one of the most dangerous species in Australia and they're mostly associated with human dwellings, which has been a problem for many years,"
The wasp is now being dubbed the "redback spider-hunting wasp" after one was observed dragging a spider it had paralyzed with a sting several yards to its nest.
"We're very excited by this discovery, which has prompted us to study this species of wasp more closely," Austin said.
"It's the first record of a wasp preying on redback spiders and it contributes greatly to our understanding of how these wasps behave in Australia."