Sex Attractant Could Control Redback Spider Spread

Thursday 25 October 2018

An acrid-smelling chemical produced by female redback spiders to attract a mate could be key to controlling a trans-Tasman invader that is threatening some of New Zealand’s endangered native insects.

The Australian redback spider, Latrodectus hasseltii has already invaded parts o

The Australian redback spider, Latrodectus hasseltii has already invaded parts of New Zealand. Image: Bryce McQuillan. All Rights Reserved

Scientists from Canterbury Museum, the University of Otago and AgResearch have identified chemicals found on the silk of virgin female redbacks. They found that male redbacks were equally attracted by virgin silk and one of the components of airborne pheromones produced by the female – butyric acid. Butyric acid is a compound chemical that gives vomit and parmesan cheese their distinctive smell.

Their research just published in the New Zealand Journal of Zoology, concludes that using pheromones to entrap and kill male spiders before they mate could be the basis for developing a way to contain redbacks.

Redback spiders were first found near Wanaka in 1981 and have expanded their range to other parts of Central Otago and New Plymouth. Climate and habitat simulations have shown that they could spread to other parts of New Zealand, including Auckland and Christchurch. Redbacks have venom that packs a serious punch and they also feed on native insects, including the endangered Cromwell chafer beetle.

Dr Cor Vink, Canterbury Museum’s Curator Natural History, says that controlling redbacks in New Zealand is a serious and difficult challenge. “We can’t use sprays as they will kill the endangered insects that we are trying to protect. Using a biological control, such as parasitic wasps, won’t work either as they would also attack katipō, which is endangered and very closely related to the redback.

“Pheromones could be the best way to control redbacks. Male redbacks offer themselves as a meal to the female while they mate. This means the male can only mate with one female. If we can trap and kill the males before they mate, we should be able to control the redback populations and their impact on our native insects.”

The next step of the research would be developing a reliable pheromone trap to attract male redbacks. “While our work has shown that male redback spiders are attracted to butyric acid, further work is need to identify the quantity and ratio of a chemical or chemicals that could be used in a pheromone trap. Our aim would be to create a sufficiently strong chemical attractant to prevent mating in an entire redback population.”

To cite this paper: Bryan SA, Vink CJ, Barratt BIP, Seddon PJ, & van Heezik Y. 2017. Investigation of two new putative pheromone components of the invasive Australian redback spider, Latrodectus hasseltii, with potential applications for control. New Zealand Journal of Zoology

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