Photo: Supplied/Morgane Merien
One of the country's top bug experts is urging people to use less pesticide and to think twice about removing trees, fearing her favourite insect is running out of places to live.
Morgane Merien, entomologist and star of TVNZ's Bug Hunter Aotearoa, says she has heard anecdotally that native New Zealand stick insects are becoming harder and harder to find.
"But like you said, it's just anecdotal, right?" she told Afternoons host Jesse Mulligan on Tuesday.
"The problem is we don't have any hard data, and we don't have historical data either to to kind of measure how those numbers may have changed over time so they could be - but it's just so hard to measure."
Where are all the stick insects?
If anyone will find out, it is likely to be Merien - she did her PhD in finding out whether stick insects look like sticks to other species.
"The way that they look has evolved to work against their predators, so animals like birds and other mammals, and they've got a really different visual system than us humans.
"So I was trying to understand better how they look like to an animal like a bird."
Birds are their biggest predators in New Zealand, "but they are now also kind of falling prey to invasive mammals like rats and hedgehogs and possums, and then the invasive wasp as well are really hitting them quite hard".
There are about 20 species of stick insect in New Zealand, all of them native.
"They're found all over New Zealand, right down from the coast, all the way up to high up in the mountains. And some species are quite specialist - they do like native plants, and then we've got other species that are kind of everywhere. There are even in your garden, on feijoa plants and strawberry plants and the like."
To hide, stick insects - as the name suggests - evolved to look like sticks, at least to us. Merien's research found birds - specifically, blue tits - see them differently to humans.
"There's different types of camouflage. The two main types are when something looks like the same background - that's called background matching - and then the other type of masquerade, that's when you look like an object and you're mistaken for that object. Those two are processed very differently in the visual systems in the brain.
"And so, with us humans, we kind of see the stick insects through background matching. We don't even realise that it's there. But with birds they do realise that something is there, but they will mistake it for something else. So their visual system is very different, and they can see colours that we can't."
A brown female Acanthoxyla stick insect. Photo: Steve Trewick
More research was required to see if that held across other species of birds, and insects - such as predatory wasps.
"[The] bird visual system is quite well preserved across lineages, but it could be that our birds see slightly different. We need more research there for sure."
She said what goes for preserving other species went for stick insects, too.
"You can just do what's good for all insects really - just try and preserve their ecosystem, really preserve their natural habitat. They're not very good disperses. So once you remove a tree that they might be on, they're very unlikely to move on to another one. They don't have wings. And kind of limit your use of insecticides and pesticides and things like that."
Asked if her research into whether stick insects look like sticks would qualify her for an Ig Nobel Prize, Merien laughed and said it would be an honour.
"That'd be great. I mean, it was definitely a really cool study to be able to do and it's got a lot of implications for biomimicry and the likes - so, you know, camouflage is used a lot within a lot of other human kind of innovation, so yeah, there's definitely applications there."
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