The bulloak jewel butterfly and how the web of life affects us all — from mistletoe to humans – Science News
The web of life is sticky, and we’re all in it.
Don Sands is craning his neck towards the dry canopies, looking for a tiny butterfly fluttering between the drought-stressed branches.
He leans a hand on the trunk of a bulloak, and gazes aloft, mouth open.
A dead mistletoe hangs off a branch.
“Look at what the drought has done to us,” he says.
For him, the dead mistletoe is a symbol of the tragic and beautiful environmental web in which we are all caught.
The bulloak butterfly
Dr Sands wears an immaculately preserved CSIRO Entomology windcheater that must be from the 1980s.
Retiring from research was never an option from him — not when there’s still so much to do — and he’s now an Honorary Fellow at the CSIRO.
He’s standing in a strip of bush near Leyburn, about 70 kilometres south of Toowoomba, Queensland, in the area of land occupied for thousands of years by the people of the Githabul dialect of the Bundjalung people.
Known as the Ellangowan Nature Refuge, this strip is the stronghold of a tiny, rare insect: the bulloak jewel butterfly.
“It lives on the bulloak but it looks like a jewel,” Dr Sands says.
“Underneath the wings you’ve got a greyish background, with little golden, silver, green and bright red spots all arranged in the most extraordinary way.”
Studying this butterfly — the second rarest butterfly in Australia — is Dr Sands’ latest project, undertaken on behalf of the Queensland Department of Main Roads and Transport.
“It’s pretty grim,” Dr Sands says.
“I spent three months here last season and I only saw five or maybe six individuals.”
“For an insect, that is drastic. That is very near the edge of extinction. You’ve only got to get one tiny problem — and we’ve got many problems, drought included — and the whole thing can go extinct.”
The importance of an ant
Dr Sands is looking for ants.
“Ah! Crush this one,” he says.
It seems, inappropriate, perhaps even sacrilegious, that this prominent insect conservationist is asking me to squash an ant between my finger and a tree.
But he wants me to smell it.
The ant’s death smells earthy, but with a tang of acid and Dr Sands says that’s how he can tell that this ant — the species, not the unfortunate individual whose life was just taken beneath my finger — is the chosen one.
“The ants pick up the caterpillars, carry them into their nests or into the hollow twigs, and they actually look after them,” Dr Sands says.
At night, the ants herd the caterpillars out to bulloak leaves — the only food that those little caterpillars will eat.
Then, in the hot daytime, the ants will steer the caterpillar back to cool safety, in hollows or lightning scars in large, old bulloak trees.
It’s a protection racket, with benefits for the ants
The caterpillars are basically defenceless, so it is incredibly beneficial to have ant childcare workers to make sure they are fed and kept safe.
The ants protect the caterpillar from parasites such as flies, which like to lay their eggs into the caterpillar, so their own babies hatch out within a smorgasbord of fresh insect guts.
“The caterpillars actually produce an attractive secretion which is made up of honey dew and that the ants really like — and that’s what attracts the ants,” says Dr Sands.
The ants like sweet nectar, like gum or mistletoe blossom. Incidentally, this is the same food that the adult bulloak jewel butterfly will require to survive.
“It’s the density of the ants that is driving this system for the bulloak jewel butterfly. And that’s how this whole place has become unique. There’s nothing else like it that we know of.”
An interwoven and dependent relationship
The butterflies are so dependent on this relationship that the ants must be present for them to reproduce successfully.
“In fact, she [the adult butterfly] won’t lay her eggs unless there’s evidence of the ants on that tree,” Dr Sands says.
Sure. Ants, they’re everywhere. Shouldn’t be a problem.
But these specific ants, which are yet to be classified with a species name, have much more complex needs that the occasional drink of sweet caterpillar wee.
They hate being underground for a start.
Don Sands points to an ant highway travelling along a line of sticks he has laid near a bulloak tree, showing how the ants prefer to avoid walking across the earth.
“They build their nests completely above ground, in old wood on the ground or in hollows in the trees,” says Dr Sands.
These are super-sized ant cities, often in huge old gum trees with satellite cities in other habitat — like the bulloaks where the bulloak jewel butterflies will be lingering.
With ant nannies in tow, the butterfly caterpillar eats bulloak leaves and grows. It will eventually pupate and become a butterfly.
And then it will only have about 10 or 15 days to find food, find a mate, find the right species of ant in the right type of tree and reproduce as many times as possible before it returns to butterfly dust.
Named, then instantly rare
Dr Sands didn’t discover the bulloak jewel butterfly. Two of his friends did.
It was the late 1960s and Dr John Kerr — actually a famous professor of pathology — and local farmer Jack MacQueen netted the very first known specimens near Leyburn.
The two men, along with Dr Sands, then worked to scientifically classify the butterfly together.
But as soon as the butterfly was scientifically christened — Hypochrysops piceata — it was instantaneously an extremely rare species.
Roads had already been cut through Queensland, land had been cleared for agriculture, towns and mining and intact bulloak woodland has been almost completely wiped out of the landscape.
“We searched high and low, right out to Goondiwindi and down to the border but we couldn’t find the bulloak jewel anywhere else.”
While the tree from which the caterpillars draw their name — the bulloak — is not rare in itself, the bulloak woodland ecosystem is listed as an endangered ecological community.
The strip of trees that forms the Ellangowan Nature Refuge near Leyburn in Queensland provides habitat for the butterfly and the ants and a glimpse of a landscape that’s almost completely disappeared.
But it’s not the rare butterfly, or even the protection of this strip of rare bushland that gets Dr Sands really steamed up — it’s the connection with agriculture.
Supporting the predators that agriculture needs
“We’ve really got to get the Federal Government more interested in preserving these [roadside] fragments,” he says of the Ellangowan Nature Refuge.
“They’re often fragments that are carrying more than just pretty butterflies. They’re carrying the beneficial organisms on which the farmers are dependent.”
Dr Sands and his colleagues in CSIRO Entomology worked for years investigating beneficial native insects in Australian agriculture.
The simplified idea is that the insect predators that live in the bushland will enter farms and suck the guts out of the pest bugs that might be on your cotton, your corn or your fodder. With these predators, you will need less sprays and will have healthier crops.
“Now if you talk to the average farmer or garden, mistletoe is a threat to the tree it’s growing on,” says Sands.
“I have a total reversal on that view.
“I’ve found mistletoe are carrying the highest biodiversity of the predators that the farmers need than any other group of plants.
“Mistletoe seems to be like a zoo of suitable prey for these native predators. So that means if you clear the bushland with the mistletoes, the bugs can’t travel from three or four kilometres away – they need to be close to the farmland.”
And the mistletoe blossom is a favourite food of the adult bulloak jewel butterfly.
The poo that carries the parasite that hosts an ecosystem
Australian mistletoes spend a life airborne on a host tree’s branch, and very briefly, inside a bird.
That bird is a flower-pecker named, helpfully, the mistletoe bird. It’s as small as a sparrow and must have one of the fastest digestive systems in the country. It’s apparently 14 minutes from go-to-whoa, and they eat any mistletoe fruit they come across.
Their poo comes out sticky and full of seeds, and — here’s an interesting thing — when they feel the urge, they turn their body along the branch rather than off it. They deposit the seed directly onto the tree instead of onto the ground, or your car below.
There are over 90 endemic species of mistletoe in Australia and many of them are tied to one particular host tree and if the right seed in the right poo is on the right species of tree and that branch has the right moisture content, among other factors, out will sprout a mistletoe: an insect zoo in the branches tree and a huge booster of biodiversity.
But the mistletoe are dying.
“There’s a stump of a dead mistletoe up there that’s died in the drought,” Dr Sands says, pointing aloft.
“That’s what we’re looking for — preferably alive.
“Where we’re working, 80 per cent of the mistletoes have died. That’s a threat to the whole system.”
And the whole system includes you, according to Dr Sands.
Six degrees of separation from you
The complexity that started with a rare butterfly has enveloped you and I, just like the ‘six degrees of Kevin Bacon’ rule.
The interconnections become so great and extend beyond the butterfly and the ant that it becomes obvious that the web of life is sticky, and we’re all in it.
To save one of the rarest butterflies in the world, you need to save an old bulloak woodland in which a lightning strike made a hole in which caterpillars can hide from the heat.
But you also need to save an unnamed ant which doesn’t like dirt, a bird who poos askew, a parasitic plant that will never touch the ground, which is home to predator insects on which farmers rely, on which you rely.
The extinction of a rare butterfly would take a tiny weight off one side of the ecological balance on which we all depend.
“When you think of the linkages – to me, the beauty is in the extension of that, to see that ultimately, we are part of that extinction. But it’s very hard to get people to see that at this stage.”