Issue 20.3: June/July 2017

Small is Beautiful

Though tiny, Hawaii’s “micromoths” are part of an epic story that spans millions of years
Story by Christie Wilcox. Photos by Chris A. Johns.

In the most remote forests of Hawai‘i live native species that most people never hear of, let alone see. In many cases species are hidden not only from adventurous hikers, but also from scientists. “A lot of these species were originally described, but then nobody has looked at them for a hundred years,” says Chris Johns, a doctoral candidate at the University of Florida who studies creatures that have been overlooked for the better part of a century: micromoths.

Micromoths would be as easily missed in a country garden as a remote jungle valley; the full-grown adults are astonishingly small: “the size of an eyelash,” Johns says. “And when I say eyelash, I mean eyelash. Certainly the length of an eyelash, and they’re maybe two eyelashes thick.” As caterpillars, the grubs are so tiny they live within the leaf. As they grow, they tunnel through the leaf, eating the tissue and leaving behind tracks called “mines”—earning micromoth larvae the common name “leaf miners.” Their mining patterns are sometimes unique to a species, so an entomologist can tell exactly what’s burrowing inside without even seeing the insect. Hawai‘i has its own special genus of micromoths, Philodoria, which is found nowhere else. Different Philodoria species are inextricably tied to the specific plants they eat, with each moth species feeding exclusively on one genus or even species of native Hawaiian plant.

Biologist Chris Johns (seen above) hikes to some of the Islands’ most remote and inaccessible areas to find Philodoria, Hawai‘i’s endemic “micromoths.”

Johns learned about Philodoria from his doctoral adviser Akito Kawahara, assistant professor and curator at the University of Florida/Florida Museum of Natural History’s McGuire Center for Lepidoptera and Biodiversity. “While he was in Hawai‘i for his postdoc, he got attached to all sorts of different Hawaiian insects,” Johns says of Kawahara, micromoths among them.“Not much had really been done scientifically, which is the case with a lot of Hawaiian insects.”

Philodoria were first described by Lord Thomas de Grey Walsingham, a British politician and amateur entomologist, in 1907. Otto H. Swezey, an entomologist with Hawai‘i’s sugar industry, developed an affection for the little insects and added more species to Walsingham’s preliminary collection. But from about the end of World War II until Kawahara arrived in Hawai‘i, Philodoria were essentially forgotten. No one knew how many species were still around. Eager to re-examine the genus, Kawahara kept his eye out for a graduate student who might be interested in Hawai‘i’s micromoths; he found that student in Johns.

The first time Johns and his team went in search of Hawai‘i’s micromoths, he found a lot of fragmented populations and several new species. “Since then we’ve been going back and slowly filling in the picture of what’s there—what’s new, what was previously undiscovered, what was once discovered and has now been extirpated or gone extinct.”

Of course, finding micromoths is no simple feat, and while there is a certain romance to being out in the field in a place as beautiful as Hawai‘i, “it’s a really tedious process,” says Johns. “We’re going hours and hours and miles and miles into the forest to try to find these things.” The first step is to find the plants that the caterpillars eat. The scientists then check the leaves for a mine, and sometimes the caterpillar is still inside. Sometimes it’s alive, sometimes dead, and “sometimes we don’t find them at all,” says Johns. Adult moths are even harder to spot. “I’ve only ever seen maybe thirty wild adult moths in my four years of doing the project. They’re just so tiny. If they fly away and leave your two-foot vicinity, then they’re lost in the forest. You just won’t ever find them again.”

Philodoria have evolved over millions of years to feed on specific native plant species, many of which grow only in remote areas like this idyllic waterfall near Wai‘ale‘ale on Kaua‘i.

Because Philodoria live exclusively on rare native plants, Johns needs help to find his bugs. Keahi Bustamante, who was working for the Plant Extinction Prevention Program on Maui when Johns met him, has been an invaluable partner; extremely rare native plants are his specialty. Johns asked for Bustamante’s help, and the two became friends. When Johns is back in Florida for his studies, Bustamante hunts caterpillars for him. To Bustamante, studying something even so tiny and seemingly insignificant as Philodoria represents an important contribution. “We’ve already lost so much of our native forests,” he says, “and the little moths and insects, they’re a huge part of what makes the forest eco-system work.”

Hidden in the leaves of the native shrub kōlea, for example, are the larvae of Philodoria auromagnifica, whose adults are breathtaking up close. “They’ve got all this silver and metallic color on their wings,” says Johns. “They’re beautiful.” His favorite species, though, is the elusive P. molo-kaiensis, which lives exclusively on the endemic Lysimachia shrub (kolokolo kuahiwi in Hawaiian) on Moloka‘i. “It’s such a beautiful moth, and it’s found only on this one Lysimachia on Moloka‘i,” Johns says reverently. “I just think it’s so cool that this organism is eking out its little existence in the mountains there, unbeknownst to most people.”

In the room that houses Bishop Museum’s entomology collection, Jim Boone lays out specimens of Philodoria from the museum’s vaults on a bench. As the museum’s entomology collection manager, Boone has worked with Johns over the past few years, giving him access to specimens collected a century ago for comparison with those he’s found recently.

Besides their diminutive size, Philodoria’s specialized diet makes them both hard to find and vulnerable. P. auromagnifica (seen above), feeds only on a rare native plant known as kōlea.

About two hundred unbelievably tiny moths are pinned, with their wings ex-tended, to a small piece of foam atop a stack of labels, each no more than a halfinch long and a quarter-inch wide, describing when, where and by whom the insect was collected. The labels accompanying the older specimens—including the first ever collected—are handwritten in implausibly small, neat cursive. “Back then they used fountain pens with India ink,” Boone explains. Recent additions are easy to spot; their labels are pristine white and printed from computer. “We now use 3.5 font size,” says Boone. Small as they are, the labels dwarf the specimens they describe. “You need a microscope to really see what they look like,” Boone says as he sets up a dissecting scope, places a minuscule brown moth underneath its lens and calls me over.

Looking in, I gasp. Magnified, the moth looks completely different. Brilliant colors dance on its iridescent wing scales in a stunning pattern. “That one is Philodoria splendida,” Boone grins. “Splendid, no? Here,” he says, switching the specimen for another, “take a look at this one.” It, too, is magnificent. Each species has a unique and colorful pattern. As Boone shows me species after species, I come to understand why Johns and the entomologists that preceded him were so taken with them.

It might seem strange that such beautiful animals would be ignored by science for so long, but in the world of entomology, like other biological disciplines, bigger, more charismatic species are the first to be described and attract more study. “For the macro butterflies, we pretty much know what most of the species are,” says Boone. Their smaller cousins have had to wait for their moment in the scientific spotlight. Despite their size, they still offer a wealth of opportunity for discoveries that might tell part of a much larger story. “There’s still a lot of work to be done,” says Boone. “We want to know: Are they still around? What’s going on with their populations? Is development taking away their habitats?”

Micromoths are easiest to see when they’re still caterpillars so small that they live between the surfaces of a leaf and chew tunnels through them, earning them the nickname “leaf miners.” Many moth larvae leave distinctive trails (like those seen above), which help Johns identify the species.

Over the past four years, Johns has started to answer some of those questions. Using genetic sequencing techniques, he and Kawahara are reconstructing the moths’ family tree to understand when the micro-moths arrived in Hawai‘i, how many species there were and how many remain. It seems the Philodoria split from their South Pacific relatives sometime between one hundred thousand and five million years ago—kind of a wide range—and Johns is working to better pinpoint when.

That means Philodoria could have arrived here even before the main Hawaiian islands existed, “which is pretty wild,” says Johns. “It was once thought that a lot of organisms endemic to Hawai‘i arrived on Kaua‘i about five million years ago and then radiated along the island chain as new islands formed,” he says. But new genetic evidence suggests that some organisms—including Philodoria, possibly—got to Hawai‘i even earlier, landing on places like Laysan Island and Kure Atoll before they became the low islands and atolls of the Northwestern Hawaiian Islands we know today. If Philodoria did come to Hawai‘i that long ago, studying their host plants and habitats could give scientists a better picture of what Hawaiian ecosystems looked like millions of years before the islands we think of as Hawai‘i rose from the sea.

Above, P. marginestrigata beside a dime for scale (Philodoria moths are never longer than five millimeters).

When Johns began the project, thirty species of Philodoria had been described. Johns has discovered more than a dozen new species, bringing the current total to forty-four. That might not seem like much for a genus of bugs, but considering that they might all derive from a common ancestor, Philodoria “exhibit the classic characteristics of adaptive radiation in Hawai‘i,” says Johns. These islands are famous for adaptive radiation, the term for when numerous species evolve from a common ancestor. Hawai‘i’s fifty-four known honeycreepers, for example, are thought to have evolved from a finch that arrived between four million and seven million years ago—perhaps the world’s greatest example of adaptive radiation among birds. The Islands’ 126 lobelia species derive from a plant that arrived about 13 million years ago, one of the most spectacular examples of plant radiation anywhere on Earth. Like the lobelias and honeycreepers, Philodoria “are one of the great Hawaiian radiations—it’s just that most people haven’t heard of them yet.”

Johns believes there are more species yet to be found. “Previous collectors probably didn’t get to plants that were extremely rare or in really remote locations,” he says, and there are still a lot of plants he hasn’t yet seen himself. At the same time, dozens of species unknown to science might now be long gone. The loss of micromoths no one has ever seen might seem like a small thing to mourn when so many species are under threat. “To some people, caring about a little moth is a little ridiculous, but I believe I came from this land, these plants, these animals,” says Bustamante, who is part Native Hawaiian. It’s right there, he says, in the Kumulipo, the ancient Hawaiian creation story. “The Kumulipo says that all the things of nature came before us and we came from them. … We are dependent on all those things of nature that came before us.”

There are currently forty-four known species of Philodoria, and Johns has discovered more than a dozen of them over the past four years. Here,
a Philodoria feeds on its host plant, nehe.

It’s an indigenous perspective that jibes with Western science. I ask Boone why these moths matter. “They’re part of the ecosystem,” he says matter-of-factly. “If you remove anything from an ecosystem, you’re going to do some harm.” That might seem obvious to a scientist, but convincing laypeople that micromoths matter is a little harder. “If you say ‘moth,’ a lot of people’s eyes glaze over,” Johns says. “Then if you say ‘microscopic moth that you’re never going to see,’ you get even more glaze. But they’re part of the story of Hawai‘i. They’re part of Hawai‘i’s biodiversity, and Hawai‘i’s biodiversity is part of Hawaiian culture.” HH