Despite the high stakes, the tiny caterpillar in the Albuquerque lab was not given a name.
It’s the last known individual of its kind, the critically endangered Sacramento Mountains checkerspot. If the caterpillar survives, it will transform into a butterfly with wings of stenciled orange, black and cream. Scientists hope to breed it by finding and capturing another from the wild, if any are left.
But last summer, as researchers prepared for weeks of searching for the subspecies in the only place on earth it might be found, the Sacramento Mountains of New Mexico, they knew that their chances of finding any were low. Despite annual surveys, it hadn’t been seen in the wild since 2022. Climate change and too much grazing have wreaked havoc on the plants that the insects need for food.
Back in 2022, four butterflies were found and collected. They bred and produced more than 160 caterpillars, but almost all died before becoming butterflies. Among the few that did transform, there was never a male-female pair alive at the same time. All died without the opportunity to breed.
By this spring, only one caterpillar was left, still in larval form three years later.
“It’s really best not to name things in this situation,” said Quin Baine, the invertebrate species survival specialist at the New Mexico BioPark Society, which supports the zoo and botanic gardens where the caterpillar is housed. “There is a level of detachment that you have to keep.”
Much would need to break in their favor to prevent the butterfly from going extinct. Still, Dr. Baine and the team of scientists and volunteers working with her couldn’t help but hope that their last-ditch conservation efforts would work.
The Sacramento Mountains checkerspot is classified as a subspecies of the broader anicia checkerspot butterfly, but some scientists believe it’s actually a separate species. Either way, over thousands of years, its mountain home acted like an island, sending the insect down its own evolutionary path. One distinguishing trait is that the caterpillars eat only New Mexico beardtongue, a purple flowering plant that is also endemic to the region.
While the normal ebb and flow of life on Earth entails some amount of species extinction, humans have drastically altered the world, sharply increasing extinction rates.
Charismatic animals like tigers and rhinos have long been a focus of conservation efforts and pleas to the public, but in recent years, alarming declines in insects have captured growing attention. Insects pollinate plants, turn dead matter back into nutrients and provide a critical source of protein and fat for all kinds of animals in the food web.
At the same time, they are poorly understood. Insect life is staggeringly diverse and wonderfully strange. Entomologists are struggling to document and understand the basic biology of species even as they are disappearing.
The Sacramento Mountains checkerspot wasn’t described in scientific literature until 1980.
“There are probably many species that have gone extinct; we’re not aware of it yet,” said David Lightfoot, a research professor who manages the arthropod collection at the University of New Mexico’s Museum of Southwestern Biology.
Dr. Lightfoot said he would see lots of the butterflies when he went to the mountains to hike, bike and collect grasshoppers for his graduate research in the late 1980s.
“They were common,” he said.
But around a decade later, a biologist at the United States Forest Service, Renee Galeano-Popp, grew concerned for the species.
She quietly reached out to Kierán Suckling, now the executive director of the Center for Biological Diversity. The group petitioned for the insect to be added to the federal endangered species list in 1999.
At first, concerns centered on threats from development and grazing, and the federal government seesawed over whether the species warranted listing. Over time, the danger from climate change grew.
Ultimately, more than 20 years would pass before federal wildlife officials classified the butterfly as endangered in 2023.
This year’s search started in June.
Over the course of the month and a half, a dozen or so biologists and other expert volunteers took turns zigzagging, literally, across meadows in the Lincoln National Forest. They divided them into quadrants and methodically poured over every part, noting every butterfly and flower. They swabbed for DNA that could signal the presence of checkerspot butterflies.
Much of the search focused on areas that were fenced to protect the plants from being overgrazed, including by feral horses. An unbalanced ecosystem created by too much grazing is a major threat to the butterflies because it depletes their food source.
According to federal wildlife officials, it’s one of five primary threats faced by the species. The others are climate change, altered wildfire regimes, invasive plants and recreation.
Arriving in the mountains in June, Dr. Baine was struck by how bad even the protected meadows looked, alarmingly dry and flowerless.
“The situation seemed dire,” she said.
A growing body of research is finding evidence that climate change is taking a heavy toll on insects, notably in the Southwest. For the Sacramento Mountains checkerspot, scientists are zeroing in on declining winter snowpack as a potential driver of declines. Last winter was New Mexico’s second driest on record.
“We have accelerated climate change to a rate that species can’t keep up with,” Dr. Lightfoot said. “That’s the problem. Natural climate change happens slow enough that populations could evolve to deal with it.”
Dr. Baine returned to the mountains with Dr. Lightfoot for surveys in July. By then, the monsoon rains had arrived and the meadows had greened.
The fenced areas were doing well.
“It looked like somebody’s flower garden,” Dr. Lightfoot said. But outside, feral horses had grazed the grass so low that “it was like a golf course.”
To Dr. Baine’s delight, one unfenced area was covered in blooms and crawling with butterflies.
But among them, the team found no Sacramento Mountains checkerspots. The surveys ended in late July without finding a single one.
“It’s our responsibility to do what we can for every other thing that lives in those mountains and that is probably threatened by the exact same situations,” Dr. Baine said.
All the while, the nameless caterpillar remained in its plastic home in a lab room in Albuquerque.
It had eaten well in the spring, but as the months wore on, researchers grew increasingly concerned. The leaves they supplied went all but untouched. The caterpillar barely moved.
“We’re kind of out of ideas for how to induce it to move on to the next life stage,” Dr. Baine said as the summer was winding down.
She believes the species is hanging on in the wild, possibly on the adjacent lands of the Mescalero Apache Tribe, where the surveys weren’t permitted.
The tribe did not respond to requests for comment.
Dr. Lightfoot fears the insect is already gone, making the caterpillar in the lab the last existing individual.
For scientists to breed the Sacramento Mountains checkerspot, either artificially or by crossing it with another subspecies, the caterpillar has to transform into a butterfly. That didn’t look likely. It wasn’t eating enough to build up fat stores for hibernation.
The caterpillar had already spent three winters hibernating in captivity. The previous fall, there had been two individuals left. When the care team tried to wake them up in the spring, only one was alive. Dr. Baine thinks the other simply hadn’t eaten enough to survive hibernation.
“I’m concerned that this one is also going to starve,” Dr. Baine said.
In a last-ditch effort, she decided to induce hibernation again, and a little early, so it would stop burning through whatever fat it had left.
“What we’re learning from this captive larva is that this butterfly can actually live for a lot longer than we previously believed,” Dr. Baine said. “They might be super-adapted at just waiting until conditions are better to complete their life cycle.”
In September, the team members caring for the caterpillar moved it to an incubator that looks like a mini-fridge and slowly brought down the temperature.
If it lives until spring, they will try to wake it up.
Catrin Einhorn covers biodiversity, climate and the environment for The Times.
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