Beetles alone make up a quarter of every named animal species we have. That’s wild on its own. But it turns out we’ve been massively undercounting. Way undercounting. A new analysis published Monday in the Proceedings of the National Academy of Sciences suggests there are actually 20 million distinct insect species on Earth. Three times more than the 6 million figure taxonomists have clung to for years.
We’ve described just 1.5 million. The rest? Ghosts.
“It’s a game changer.” Nigel Stork says this. He’s an entomologist at Griffith Australia and helped set those lower estimates way back. He calls the new work “amazing.” He’s not alone. The math is solid. The implication is heavy.
But how do you count the invisible? You can’t just poke around in the dirt and hope. It took decades of hunting parasitoids in Costa Rican cloud forests. It borrowed lessons from hepatitis A outbreaks in Taiwan colleges. It required a global map of trees. Strange ingredients. But the recipe worked.
The goal wasn’t to catch everything. It was to estimate how much we were missing.
Let’s look at the wasps first. Specifically parasitoids. The scary ones. They hatch inside other creatures. They burst out. Alien style. Guzman’s team looked at three long-running tracking projects in Costa Rica. Two used Malaise traps. Think tent-shaped nets catching flying bugs funneling them into liquid for preservation. The third was slower. Grimmer. Dan Janssen and Winnice Hallwachs spent forty years collecting caterpillars. Raising them. Waiting. They wanted to see which wasps would tear their way out of the larvae flesh.
The results were stark. Across all three methods they found 1414 wasp species. Almost zero overlap. Nearly thirty percent were single-observation records. Seen once. Gone forever. That lack of repeat sightings told the lead author Robert Colwell something vital. They aren’t even close.
Colwell is an entomologist and a statistician at the CU Museum of Natural History. He knew they needed a new way to look at the gap between observed and unobserved. They turned to disease tracking. Remember hepatitis B? In 2015 co-author Anne Chao looked at blood serum tests doctor reports and student questionnaires. She mapped the overlaps. And the gaps. She estimated the true size of the outbreak. The same math applied to wasps. The true number in the park wasn’t 1400. It was closer to 3400.
That ratio mattered. They applied it to the “bug soup” from the Malaise traps. That stuff contained 1.6 million individual insects. DNA barcoding identified 54000 species. If wasps were being underestimated by a certain factor why wouldn’t other bugs be too? They ran the numbers. The ballpark estimate for insect species in that specific Costa Rican park? 333000.
A big number for a patch of jungle. But this is only the beginning. The team needed a global anchor. Trees provided it. “Latitudinal richness” is the rule here. Biodiversity peaks at the tropics. Fades near the poles. True for every kingdom. True for plants too. Trees are well-mapped. Insects are not. The researchers used a grid-map of global trees to calculate an “upscaling factor.” From Costa Rican tree counts (around 1500) to worldwide counts (about 73300) they bridged the gap.
The result hits you in the chest. 20 million insect species. Many with adaptations we’ve never seen. Behaviors we can only imagine.
It changes how we think about conservation. “It makes it obvious” Colwell says. Traditional taxonomy can’t keep up. There aren’t enough people with microscopes. Not within our lifetimes anyway. We won’t name them all. We likely never will.
But knowing the scale of the unknown helps. “It’s really useful to know who shares Earth with us.” Guzman’s point lands hard. Biodiversity is under threat. This new baseline gives us a reference. It tells us exactly how much we might lose before we’ve even met them.
