Female redback spider. Photo: Wara Bullôt / © Plant & Food Research. All rights reserved.
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The 'Pūngāwerewere Workroom' at Plant & Food Research is not a happy place for anyone with arachnophobia - a fear of spiders.
But it is a happy home for the 800 Australian redback spiders who live here, each in their own individual spider 'apartment', with hand-delivered meals of fruit flies or crickets every week.
These spiders are unwitting helpers in a plan to set a trap for their own kind.
The key to that trap: an irresistible spiderweb perfume.
Andrew visits the spider "apartments". Each redback spider has its own spider apartment, housed within a second larger box for extra security. Photo: Ellen Rykers / RNZ
A sneaky, smelly trap
To try to control unwanted redback spiders, a team of scientists has devised a cunning concept for a redback trap that relies on a pheromone (chemical signal) lure.
The idea is to attract redback males to the trap with the scent of virgin female spiderweb.
First, the researchers must figure out exactly what alluring compounds are wafting off the web.
A vial containing 10 webs' worth of virgin redback silk. Photo: Ellen Rykers / RNZ
"What we've been doing is collecting lots and lots of that virgin silk so we can analyse the odours coming off it, which the males are then attracted to," said Dr Andrew Twidle, a chemist at Plant & Food Research.
"We can see a really clear signal from that virgin silk that the boys really like and head to."
By identifying the tantalising cocktail of smells, Twidle and his team will then be able to whip up humanmade batches of spiderweb perfume in the lab.
Sniff tests in the spider arena
The next step was to test the attractive power of the synthetic spiderweb scent in the 'spider arena'.
Andrew with the y-shaped tube and "spider arena" set-up where different variations of the spiderweb perfume are tested. Photo: Ellen Rykers / RNZ
A male spider is placed at the end of a Y-shaped glass tube, with two different odours drifting down each arm of the Y.
"They'll go, 'oh, I can smell something I like'. And they start waving their little front legs around... and then they'll pick the one they like," Andrew says.
Once the team gets the spiderweb aroma just right, they'll start testing it in the field and designing a 3D-printed dispenser.
The trap will also function based on size. Male redback spiders are only about the size of a pinhead, meaning the trap can exclude any larger creatures.
The male redback spider (left, in the vial) is much smaller than the female redback spider (right, in the jar). Photo: Ellen Rykers / RNZ
"We don't want to accidentally catch other ground dwelling insects," Twidle said. "So we need to have excluding factors, while maintaining an enticing entrance for the male spider."
Why get rid of redbacks?
Redback spiders are native to Australia but made their way to New Zealand in the 1980s.
There are currently two populations: one in Central Otago, and one in New Plymouth.
Redbacks can deliver a venomous bite that causes severe pain, vomiting and sweating in humans. Luckily, a bite isn't usually life-threatening - especially with antivenom now stocked at hospitals across Aotearoa.
Still, redback bites pose a health risk and threaten endangered native species.
The Aussie invaders prey on the Cromwell chafer beetle, a 'nationally critical' species found in a single reserve near Cromwell, and can hybridise with native katipō, also a threatened species.
A redback spider consuming its hand-delivered meal, as viewed through a microscope. Photo: Ellen Rykers / RNZ
Listen to the episode to learn more about the redbacks' wild mating habits, how the species has rapidly spread across Japan, and the team's future plans for the spider trap.
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