Some scientists warn of an insect apocalypse. The flying-insect community has been “decimated,” a research paper said. Illustration by Jochen Gerner

Insects were among the first regular features in these pages, thanks to Milo’s camera and personal interest. There were more when Seth worked in Costa Rica, followed by plenty of articles and editorials of various types, as well as my own discoveries while working outside. Looking back over those, I notice that caterpillars were featured only once, in a post on integrated pest management. So the following is a welcome addition to the mix:

The Little-Known World of Caterpillars

An entomologist races to find them before they disappear.

The Devils River, in southwestern Texas, runs, mirage-like, along the edge of the Chihuahuan Desert, through some of the most barren countryside in the United States. Access to the river is limited; unless you’re in a kayak, the only way to travel upstream is along a skein of rutted dirt roads. It was on one of these roads that, a few years ago, David Wagner noticed a shrub that seemed to him peculiarly filled with promise.

Wagner is an entomologist who teaches at the University of Connecticut. He has close-cropped silvery hair and a square jaw and bears a passing resemblance to George C. Scott playing General Buck Turgidson. The way other people might recall a marvellous restaurant or a heartbreaking vista, Wagner remembers a propitious plant. He has friends who own a house along the Devils River, and each time he has visited them he has stopped by the exact same shrub to investigate. No luck. This past October, I was travelling with him when he tried yet again. He spread a white nylon sheet on the ground, then started whacking the bush with a pole to dislodge anything that might be clinging to it.

“Un-fucking-believable!” he exclaimed. I was whacking a plant nearby, just for the hell of it. Wagner held out his hand. A caterpillar about three-quarters of an inch long was wriggling across his palm. It looked brownish and totally ordinary until I examined it under a loupe, at which point it was revealed to be flamboyantly striped, with yellow and red splotches and two black, hornlike protuberances sticking out of its back. Based on a series of taxonomic calculations, Wagner was convinced that the caterpillar was the juvenile form of an exceptionally rare moth known as Ursia furtiva.

“No one’s ever seen this before,” he told me. If Wagner was the first person to lay eyes on an Ursia furtiva caterpillar, I figured, that meant I was the second. Un-fucking-believable.

Caterpillars are to lepidoptera—butterflies and moths—what grubs are to beetles and maggots are to flies; they are larvae. Even among nature lovers, larvae tend to be unloved. For every ten butterfly fanciers, there are approximately zero caterpillar enthusiasts. The reason for this will, to most, seem obvious. The worm in the apple is usually a caterpillar.

Wagner specializes in caterpillars, or, it might be more accurate to say, is consumed by them. (They are, he suggested to me, the reason he is no longer married.) Probably he knows more about the caterpillars of the U.S. than anyone else in the country, and possibly he knows more about caterpillars in general than anyone else on the planet. When he travels, it’s not uncommon for him to return home with a suitcase full of specimens. Most of these he has injected with alcohol; some, though, may remain alive, nestled in little vials of their favorite plants.

Wagner’s “Caterpillars of Eastern North America,” published in 2005, runs to nearly five hundred pages. It relates the life histories of roughly that many species and is considered the definitive field guide on the subject. Wagner is now thirteen years into an even more ambitious project, “Caterpillars of Western North America,” which he plans to publish in four volumes.

The implicit argument of Wagner’s work is that every larva matters, no matter how small, squishy, and unassuming. Each new species that he collects is a different answer to life’s great conundrum: how to survive on planet Earth. Each has a unique and often startling story to tell.

“I want to write each species account so you want to read one more,” he told me. “I want it to be a page-turner.”

Wagner, who is sixty-six, grew up pretty much all over the place. His father, a metallurgist, worked for U.S. Steel, and the family moved whenever he was assigned to a new project—a bridge in one state, a pipeline in another. In second grade, Wagner attended three different schools. “I don’t know where I’m from,” he told me. At one school, in Missouri, he remembers, he was greeted by kids throwing rocks at him…

Read the whole article here.