Near the center of the old city, a paper sign, not much larger than a business card, identifies the stolid headquarters of the society whose research caused so much commotion. When it was founded, in 1905, the society operated out of another building, one that was destroyed when Britain bombed the city during World War II. (By the time the bombs fell, members had moved their precious records and collections of insects, some of which dated back to the 1860s, to an underground bunker.) Nowadays, the society uses more than 6,000 square feet of an old three-story school as storage space. Ask for a tour of the collections, and you will hear such sentences as “This whole room is Lepidoptera,” referring to a former classroom stuffed with what I at first took to be shelves of books but which are in fact innumerable wooden frames containing pinned butterflies and moths; and, in an even larger room, “every bumblebee here was collected before the Second World War, 1880 to 1930”; and, upon opening a drawer full of sweat bees, “It’s a new collection, 30 years only.”

On the shelves that do hold books, I counted 31 clearly well-loved volumes in the series “Beetles of Middle Europe.” A 395-page book that cataloged specimens of spider wasps — where they were collected; where they were stored — of the western Palearctic said “1948-2008” on the cover. I asked my guide, a society member named Martin Sorg, who was one of the lead authors of the paper, whether those dates reflected when the specimens were collected. “No,” Sorg replied, “that was the time the author needed for this work.”

Sorg, who rolls his own cigarettes and wears John Lennon glasses and whose gray hair grows long past his shoulders, is not a freewheeling type when it comes to his insect work. And his insect work is really all he wants to talk about. “We think details about nature and biodiversity declines are important, not details about life histories of entomologists,” Sorg explained after he and Werner Stenmans, a society member whose name appeared alongside Sorg’s on the 2017 paper, dismissed my questions about their day jobs. Leery of an article that focused on him as a person, Sorg also didn’t want to talk about what drew him to entomology as a child or even what it was about certain types of wasps that had made him want to devote so much of his life to studying them. “We normally give life histories when someone is dead,” he said.

There was a reason for the wariness. Society members dislike seeing themselves described, over and over in news stories, as “amateurs.” It’s a framing that reflects, they believe, a too-narrow understanding of what it means to be an expert or even a scientist — what it means to be a student of the natural world.

Amateurs have long provided much of the patchy knowledge we have about nature. Those bee and butterfly studies? Most depend on mass mobilizations of volunteers willing to walk transects and count insects, every two weeks or every year, year after year. The scary numbers about bird declines were gathered this way, too, though because birds can be hard to spot, volunteers often must learn to identify them by their sounds. Britain, which has a particularly strong tradition of amateur naturalism, has the best-studied bugs in the world. As technologically advanced as we are, the natural world is still a very big and complex place, and the best way to learn what’s going on is for a lot of people to spend a lot of time observing it. The Latin root of the word “amateur” is, after all, the word “lover.”

Some of these citizen-scientists are true beginners clutching field guides; others, driven by their own passion and following in a long tradition of “amateur” naturalism, are far from novices. Think of Victorians with their butterfly nets and curiosity cabinets; of Vladimir Nabokov, whose theories about the evolution of Polyommatus blue butterflies were ignored until proved correct by DNA testing more than 30 years after his death; of young Charles Darwin, cutting his classes at Cambridge to collect beetles at Wicken Fen and once putting a live beetle in his mouth because his hands were already full of other bugs.

The Krefeld society is volunteer-run, and many members have other jobs in unrelated fields, but they also have an enormous depth of knowledge about insects, accumulated through years of what other people might consider obsessive attention. Some study the ecology or evolutionary taxonomy of their favorite species or map their populations or breed them to study their life histories. All hone their identification skills across species by amassing their own collections of carefully pinned and labeled insects like those that fill the society’s storage rooms. Sorg estimated that of the society’s 63 members, a third are university-trained in subjects such as biology or earth science. Another third, he said, are “highly specialized and highly qualified but they never visited the university,” while the remaining third are actual amateurs who are still in the process of becoming “real” entomologists: “Some of them may also have a degree from the university, but in our view, they are beginners.”