Life at the Top
Story by A. Kam Napier
Photos by Josh McCullough
Four men move slowly over a field of reddish-black cinder, eyes downcast, with the body language of people searching for a dropped contact lens. Loosely packed gravel extends as far as the four can see— which, on this sometimes rainy, sometimes snowy afternoon on the summit of the Big Island’s Mauna Kea, is all of fifty yards. They keep their eyes peeled for their quarry, which is likely hiding somewhere within the gravel crunching beneath their cautious steps: the wekiu bug.
First discovered a little more than thirty years ago, the flightless wekiu bug is no bigger than a grain of rice —and not much different in shape if a grain of rice had six skinny legs attached to it. The wekiu bug, formally known as Nysius wekiuicola, exists nowhere else in the world but the summit of Mauna Kea, and hence its name: wekiu, which in Hawaiian means the top or summit. The insect has adopted a suite of survival skills for the summit’s harsh, cold climate, the most striking of which is its transformation from vegetarian to carnivore: While its closest Hawai‘i relatives live off seeds, the wekiu bug has become a scavenger that feasts on windborne insects that are blown up to the summit and immobilized by the cold.
One of the men overturns a stone the size of a softball and calls out for the expedition leader—University of Hawai‘i at Hilo entomologist Jesse Eiben—to take a look at what he’s found. Eiben, his slight build encased in a sturdy windbreaker, is gently scooping a hole out of the cinder, looking for a spot where a wekiu bug might be hiding from the cold. He stands, takes a look at the proffered rock and shakes his head. “That’s a Nysius, all right,” he says, pointing to the dried-out bug on the rock that the man has found, “but not a wekiu bug.” Eiben, one of just half a dozen or so people in the world who could be considered an expert on the wekiu bug, points to the pronounced wings of the insect carcass, which, he says, give it away instantly as a non-wekiu bug. “Good ento skills, though!” he says with a consoling chuckle.
That laugh is not unusual. Eiben laughs often, almost as a kind of punctuation. In his emails he laughs with emoticons. After a weekend tagging along with him on the Big Island, I’m convinced it’s the chuckle of a person in love with his work.
Eiben had warned us not to get our hopes up as we trudged from the warmth of the state-owned SUV up the slope in search of the wekiu bug. “They’re usually pretty inactive when it’s really cold,” he’d said. Regardless, even if we weren’t seeing the wekiu bug, we were seeing its entire universe: rolling pu‘u, or hills, of loose cinder thousands of feet above sea level.
The Mauna Kea Arthropod Biodiversity Project collaborates with UH Hilo’s Office of Mauna Kea Management to keep tabs on which species at the summit are native, which are not and how the native species are faring. Eiben runs the project with UH Manoa entomology professor Dan Rubinoff; together with three undergraduate students, they’ve collected and cataloged some ten thousand insects from the alpine region of the summit.
Yes, the wekiu bug is not alone in its lair; it is one of fifteen endemic species of arthropod at the summit, a group that also includes spiders, a centipede, various mites, bark lice, moths and beetles. Non-native species, from minuscule flies to butterflies and moths, get blown to the summit regularly. Once there they usually succumb to the cold, but there are now newcomers living on Mauna Kea. Says Eiben, “I estimate [about] ten to fifteen non-Hawaiian arthropods may be at the summit on a year-round resident basis.” These include predatory beetles, spiders and omnivorous true bugs, which are distant relatives of the wekiu bug.
For the wekiu bug, soil is everything. It lives only amid a loosely aggregated layer of scoria or tephra at about an eleven-thousand- foot elevation and above. Individual bits of this soil resemble petrified froth, formed when gas escaping from volcanic vents blows droplets of magma into the air. The magma solidifies as it cools in midair and falls back to earth like stone snow. Little pieces, up to an inch, are called gravel; bigger pieces from one to four inches across are called cobbles.
Eons of these volcanic sneezes produced hill-size piles of tephra around individual vents — the pu‘u that Mauna Kea is known for. The 13,796-foot volcano was further shaped by glaciers, which thousands of years ago sculpted its summit and cut the cinder cones, further defining the area where the wekiu bug now lives. Where glaciers scoured the vast, flat expanses between the pu‘u clean of tephra, wekiu bugs are usually not found. The wekiu bug’s favorite environment on the summit is amid a layer of tephra six to ten inches deep and comprised of both gravel and cobbles— in that very specific habitat, wekiu make their home.
Wekiu bugs are classified in the order Hemiptera, or true bugs; there are as many as eighty thousand Hemiptera species worldwide. “What they all have in common is really long mandibles,” says Eiben. Everyday names for species within Hemiptera include stink bugs, squash bugs, assassin bugs, even bedbugs. Many are considered pests. Within the order Hemiptera is the family Lygaeidae. All of the bugs in this family are seed bugs, and there are about five thousand species— including the wekiu bug. Seed bugs are small, teardrop-shaped insects, usually winged, with rounded abdomens that taper to narrow heads. They typically use their needle-like, sheath-covered mandibles to penetrate the skins of seeds or plants.
The Lygaeidae family houses the Nysius genus, of which there are some 106 species worldwide—with twenty-six of those, including Nysius wekiuicola, found only in the Hawaiian Islands. “Perhaps five and a half million years ago, the first Nysius blew to Kaua‘i, hung on and survived,” says Eiben. Once here, it evolved to take advantage of different niches in the ecosystem, something that has happened again and again in the Islands. There are approximately ten thousand species of endemic insects in Hawai‘i, all descended from just three to four hundred lineages.
Given the wekiu bug’s rarity and habitat, there is much still to learn about its daily life, and some of what people think they know, says Eiben, is wrong. “Sometimes you hear that it has evolved a natural antifreeze in its blood to keep from freezing at the summit,” he says. “That’s just not true.” But the wekiu bug has adapted for the cold in some ways. Its wings are vestigial; they would be a waste of energy now because it doesn’t use them. And its unusually long legs are an essential tool in tending to its body temperature and hydration. Wekiu bugs need the sun to keep warm and can be seen basking on rocks in the day from about March to October. But even when the air is below freezing, solar energy can heat the rocks to temperatures above 100 degrees. Those stilt-like legs help the bugs keep a safe distance off the rock so they don’t cook. When temperatures drop at night and it’s too cold to be out, the wekiu bugs crawl into the comparatively warm voids of the tephra to avoid freezing and to find the moisture trapped there.
Eiben knows, from raising a colony of wekiu bugs in the lab from 2006 to 2009, that they can live just fine at other temperatures. They’re typically more active in the spring and summer, when they find mates, with females laying eggs that hatch nymphs. These nymphs will molt several times as they grow to full size.
But the summit’s where the food is and where the wekiu’s remarkable adaptation as a carnivorous scavenger works best. As much as it needs the sun to keep warm, it needs the cold to kill or stun its prey. Wekiu bugs have been found at the edge of snowmelts, where windborne insects fall like frozen dinners. They have been seen feeding on insects much larger than themselves, penetrating their exoskeletons, injecting digestive enzymes, then sucking up nutrients and moisture.
Eiben recalls a particularly fat time for the wekiu bug last year, when an outbreak of koa looper moths erupted on the Big Island. Their caterpillar forms defoliated fifty thousand acres of native koa trees between February and June 2013, then turned into millions of moths, many of which were blown upward. “There were just piles of them all around the summit,” he recalls. Of course, it isn’t all just koamoths- from-heaven. It works the other way, too: Native centipedes and wolf spiders both eat the wekiu bug.
Given that the Big Island is only half a million years old, the wekiu’s switch from winged seed-eater to nearly wingless scavenger seems remarkably fast. “There’s a really good likelihood that Haleakala had a transitional form of the bug,” Eiben speculates; the Maui volcano is an estimated 1.1 million years old.
Managing the arthropod project, teaching, consulting on invasive species—these take up the bulk of Eiben’s time now, but from 2005, when he arrived in Hawai‘i as a PhD research assistant, to 2012, when he graduated, 100 percent of his attention was focused on the wekiu bug. In part that was because a lot of people were looking for answers about the wekiu bug. Thirteen different telescopes and observatories have been built on Mauna Kea since 1970, and another, the forthcoming Thirty Meter Telescope, will be the world’s largest; its construction, begun last year, is projected to last until 2020. General visitation to the summit has increased, too, with sightseers, mountain bikers and hikers now dotting the summit access roads, any of whom could alter the wekiu bug’s environment or unwittingly introduce invasive species.
Early surveys of wekiu bug showed small, even declining populations, and the bug was a candidate for protection under the Endangered Species Act. In 2003 KAHEA, the Hawaiian-Environmental Alliance—a group opposing further telescopes on the summit — petitioned the US Fish and Wildlife Service to formally list the bug as endangered and the summit as its critical habitat.
But that didn’t happen. The wekiu bug was removed from the list of candidate species for protection in 2011. In the years before, scientists at Bishop Museum, UH and those hired to do surveys for the telescopes had done research, compared notes and concluded that there was no evidence that the bugs’ populations were declining. “In fact, they live quite well in the loose cinder that’s been pushed aside right next to the telescopes,” says Eiben, who testified in court that the wekiu bug seemed able to withstand a certain amount of development. His experience running a colony of wekiu bugs in the lab (in conditions matching those of the summit) had convinced him that the population could “theoretically double every fifteen days.”
So: How many wekiu bugs do live on the summit? Eiben has worked to perfect techniques for trapping and counting the wekiu, but given the uncertainty inherent in collecting them, he suggests somewhere between forty-six thousand and ten million. That, he writes in an email, is “about as comfortable as my data is right now ;).”
Down below the wekiu bug’s lowest range, on the way to Mauna Kea’s Hale Pohaku station at nine thousand feet, Eiben notes that half the species in this alpine shrub-land are introduced. “That’s Madagascar fireweed,” he says, pointing out a colander-sized clump of yellow flowers. “It’s not from here.” Problem is, it attracts aphids, every one of which is an introduced species in the Islands. The aphids draw ants, which are also introduced; there’s not a single native species of ant anywhere in the Islands. If ants get to the summit, scientists believe they’re bound to have a negative effect on the wekiu bug.
So Eiben sometimes joins other volunteers pulling up the
fireweed. As we drive down the volcano, he notes that much of entomology is
driven by economics. Of the one million known insect species in the world, only
a few thousand have been thoroughly studied—almost always because they needed
to be controlled or eliminated in the ancient battle between humans, who want
to grow their food, and insects, which show up to take it first. Eiben
considers it a rare and wonderful thing to be one of the people keeping an eye
on the summit of Mauna Kea, watching for signs that the wekiu bug and its
fellow native species might be disturbed by outside forces. “It’s not very
often,” he says, “that you get to study an insect in order to save it.”