'Butterfly Tongues' Are More Ancient Than Flowers, Fossil Study Finds

Jan 10, 2018
Originally published on January 10, 2018 10:55 pm

Butterfly beak. Moth mouthpiece. Lepidoptera lips.

Call it whatever you want, the proboscis is a big deal. It's a defining feature of many moths and butterflies – the long, flexible mouthpiece that dips into flowers and draws out nectar.

"The traditional idea is always [that] this proboscis — this butterfly tongue — is a standard adaptation you have when you feed on flowers," says Timo van Eldijk, a researcher at Utrecht University in the Netherlands who is an author of a new study in Science Advances that upends traditional ideas about the proboscis.

"What we found is that there were moths and butterflies with a proboscis that were already around way before there is evidence of flowering plants," he says.

The discovery hinges on fossils recovered from German soil cores — the oldest fossils of their kind. Butterfly and moth remains are rarely fossilized, in part because they're delicate. But van Eldijk, a masters student, found he could isolate fossils of the microscopic scales that coat insects' wings and bodies. The tiny scales also give butterflies their colors.

"If you touch the wing of a butterfly, you will very often see that the color tends to fade," he explains. "That's the scales coming off the wing."

Van Eldijk spent weeks finding 70 scales that were embedded in the ancient soil, teasing each one out using a needle tipped with a human nose hair (something about its tensile strength makes it the perfect tool for this particular task). Then, he used microscopes to analyze the structures of the scales.

He found some of the scales, from about 200 million years ago, were hollow. The only butterflies and moths with hollow scales are a group called Glossata, which all have proboscises.

"The most exciting thing was the hollow scales," explains van Eldijk. "If you find the hollow scales, you know the innovation of the proboscis must have occurred before that."

The findings mean that butterflies and moths with proboscises are 70 million years older than had previously been demonstrated with fossil evidence.

The research corroborates molecular studies that suggested similar findings, says Fabien Condamine, a longtime butterfly researcher at Universite de Montpellier in France. Condamine wrote in an email that the study is important because there are so few fossil discoveries on the topic, but that the implications for the entire field are somewhat moderate.

"This is a really exciting paper," wrote butterfly expert Niklas Wahlberg of Lund University in Sweden in an email, noting that he was particularly impressed by the "amazingly detailed pictures," including images of individual microscopic scales.

Both noted that there are more questions to be answered about the origins of the proboscis. For example: What were moths and butterflies using these long tubes for, if there weren't any flowers?

Van Eldijk has two theories. Perhaps, he says, they were using them to lap up droplets from the surfaces of plants' cones, or maybe it helped them stay hydrated in the arid prehistoric climate.

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KELLY MCEVERS, HOST:

We usually see butterflies hanging out around flowers and drinking nectar, but scientists have made the startling discovery that there were butterflies long before there were many flowers. NPR's Rebecca Hersher reports that scientists found this out by studying fossilized bits of butterfly from millions of years ago.

REBECCA HERSHER, BYLINE: Butterflies are really delicate creatures, so they don't preserve well, which means there aren't that many complete fossils. But a team looking at soil from Germany stumbled upon fossils of tiny butterfly scales. Scales give butterfly wings their colors.

TIMO VAN ELDIJK: If you, like, touch the wing of a butterfly, you will very often see that the color tends to fade, and that's actually the scales coming off the wing.

HERSHER: This is Timo van Eldijk over Skype. He's a master's student in the Netherlands and one of the authors of a new study published today in the journal Science Advances. He says these are the oldest butterfly fossils ever discovered, from the Jurassic period about 200 million years ago. But the most exciting thing was what van Eldijk saw when he looked at the scales under a microscope. Some of them were hollow, and that can only mean one thing - that prehistoric butterflies had proboscises. That's basically a butterfly's trunk.

ELDIJK: If you find the hollow scales, you know that this innovation of the proboscis must have already occurred before that.

HERSHER: There's no way to have hollow scales if you don't have a proboscis.

ELDIJK: No, no.

HERSHER: But here's what's weird about that - modern butterflies only use their proboscises to suck up nectar from deep inside flowers.

ELDIJK: The traditional idea is always butterfly tongue is your standard adaptation that you have when you feed on flowers, right?

HERSHER: But that can't be right because the ancient butterflies with the hollows scales and the proboscises were flying around long before there were any flowering plants on Earth. So what were butterflies using their tongues for - hard to know. They might have still used them to eat, maybe droplets on the surface of cones instead of flower nectar. Or maybe the tongue helped them stay hydrated. The Jurassic, after all, was a pretty dry time. Rebecca Hersher, NPR News. Transcript provided by NPR, Copyright NPR.