Scientists are investigating a potential new biological control for one of New Zealand's most voracious pasture pests, the grass grub.
Researchers from the Foundation for Arable Research (FAR) made the discovery in Southbridge, Canterbury when they found grass grub pupae being eaten alive by maggots.
They identified the maggots as the larvae of a little known native carnivorous fly.
FAR research manager Richard Chynoweth said the discovery was a surprise, because it is the first evidence they have seen that the fly is a predator of grass grub.
And that raises the question of whether it could be used to help control one of the country's most costly agricultural pests.
"If we can get the populations of adults and then get a reasonable population of larvae it could be useful."
He said where the larvae was found at the site in Canterbury grass grub numbers were reduced by 30% to 50%.