Small leafy boy. Credit: Wikimedia Commons
Insects may be far more numerous than anyone thought.
A new study estimates that Earth holds 14 million to 20 million insect species, far above the long-standing estimate of about 6 million. It follows that scientists have named only a small fraction of the planet’s most diverse animals, even as reports warn that many insect populations are shrinking.
Impossible to Count Exactly
The flying termite swarm came, as was foretold. Credit: Wikimedia Commons
Counting and describing insects has always tested science’s patience. That’s why the best entomologists are investigative, meticulous, and deeply curious.
Many species look nearly identical. Others live in small ranges, pass through several life stages or appear only at certain times of year. Scientists have formally described about 1.2 million insect species, according to Cornell University. But each new survey tends to reveal more.
“We cannot protect species if we don’t know that they exist, and so to be able to understand the biodiversity on our planet, it’s important to know how many there are,” said Laura Melissa Guzman, an entomologist at Cornell University and corresponding author of the paper.
The team turned to the Área de Conservación Guanacaste (ACG), a protected region in northwestern Costa Rica that spans 169,000 hectares. It includes dry forest, cloud forest, and rainforest—a rich testing ground for insect life.
Researchers drew on more than 1.6 million tropical insect specimens collected from 15 core Malaise traps—tent-like nets that catch flying insects. They used DNA barcoding, a method that reads a short stretch of genetic code to help identify species. Those traps alone yielded close to 54,000 insect species.
Then the scientists narrowed their focus to Microgastrinae, a highly diverse group of tiny parasitoid wasps. These wasps lay eggs inside caterpillars. Their larvae hatch, feed inside the host, and later emerge.
Statistically, a Lot
A female braconid wasp from the studied family of parasitoid wasps. Credit: Wikimedia Commons
The researchers used three sources to sample the wasps: the core Malaise traps, a second set of peripheral traps, and wasps reared from about 1,500 caterpillar species. Together, the samples produced 1,414 Microgastrinae species.
From there, the team used statistical methods to estimate how many wasp species in the ACG remained unseen. They applied that ratio to the broader insect sample and estimated that the protected area may contain nearly 333,000 insect species.
To scale up from Costa Rica to the world, the researchers compared ACG diversity with global diversity in several other groups, including trees, frogs, birds and saturnid moths. That calculation led to the global estimate of 14 million to 20 million insect species.
“Our study provides a baseline to understand how much more we need to learn about insects. We need this baseline to understand the scope of current insect declines,” Guzman told Gizmodo.
Co-author Michael Sharkey, a taxonomist who specializes in describing insect species, helped shape the approach. Many past estimates relied on beetles, often described as the most diverse insect group. Sharkey’s work with Costa Rican parasitoid wasps suggested that these tiny specialists could offer a sharper, more informative proxy of overall insect species numbers.
The researchers even describe their numbers as conservative.
“Our estimate is a lower bound. We took a lot of effort at every step to evaluate our assumptions to understand whether we could be over or underestimating this lower bound,” Guzman added.
The Nameless Ones
Credit: Pexels
The new estimate arrives as scientists debate the scale of global insect decline. Some studies have warned of an “insect apocalypse,” driven by habitat loss, pesticide use, climate change, and other human pressures.
A larger insect total does not make those losses less serious. It may make them harder to see.
“Our results point to a large number of undescribed insects, those without a name,” Guzman said. “With recent reports of insect declines, there could be many species that are declining that we haven’t even discovered.”
Governments and researchers can monitor birds, mammals, and trees more easily because many have names, maps and long-term records. Insects often lack all three.
The ACG data set may help. Because researchers have collected insects there for decades, scientists can now ask whether species have grown rarer, shifted their ranges, or disappeared from traps over time.
“That gives us a window into whether populations are growing, shrinking, or shifting in response to climate change and land use,” Guzman explained. “Getting a better count of how many species exist is the first step. Understanding what is happening to those species over time is the next one.”
The study does not close the census of insect life. It widens it.
The next step is to track them before they disappear from places scientists have never searched. A larger estimate changes the scale of the task: many species may be declining before they have names, records, or a place in conservation plans.
The study was published in the journal Proceedings of the National Academy of Sciences.