Predator And Prey: Tiny Wasp Hunts Venomous Redback Spider
September 12, 2012

Centuries Old Australian Wasp Is Redback Spider’s Worst Enemy

Lee Rannals for - Your Universe Online

Even Australia's most common dangerous spider is no match for a nearly forgotten 200 year old flying insect, according to recent findings.

The wasp, Agenioideus nigricornis, was first discovered in 1775 by Danish etymologist Johan Christian Fabricius. Recently, researchers from the University of Adelaide said the small wasp is a predator of the redback spider.

"Since then, scientists have largely forgotten about the wasp," said Professor Andy Austin from the University of Adelaide's Australian Centre for Evolutionary Biology & Biodiversity. "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."

A wasp was spotted by 9-year-old Florian Irwin dragging a redback spider several feet to its nest, and his father, Dr. Peter Irwin, photographed the event.

Peter, an Associate Professor at Murdoch University, contacted the Western Australian Museum about the discovery. The museum then alerted Austin and research fellow Dr. Lars Krogmann at the University of Adelaide.

"The Museum knew we were doing research into the Agenioideus, which belongs to the family Pompilidae, the spider-hunting wasps. Little is known about them, despite various species of Agenioideus being distributed throughout the world," Austin said.

"We're very excited by this discovery, which has prompted us to study this species of wasp more closely. 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."

An adult redback spider hunting wasp is no bigger than its prey, but its sting is able to paralyze the redback spider so it can drag it back to its nest, where it lays an egg on it.

The spider remains alive, but is paralyzed, and once the egg hatches, the larval wasp feeds on the spider.

"The redback spider is notorious in Australia, and it has spread to some other countries, notably Japan and New Zealand. 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," Professor Austin said in the release.

"The redback spider-hunting wasp is doing its part to keep the population of redback spiders down, but it doesn't hunt all the time and is unlikely to completely eradicate the spiders."

The researchers have published a paper about the redback spider's predator in this month's issue of the Australian Journal of Entomology.