Scientists have identified only a small fraction of Earth’s insect species, and the true number could be far higher than previously thought, according to a study published on Monday in the journal Science.
Researchers estimate there may be as many as 20 million insect species worldwide, compared with about 1 million formally described species and a long-standing scientific estimate of roughly 6 million.
The study, published in the Proceedings of the National Academy of Sciences, used statistical modeling based on insect surveys in Costa Rica’s Guanacaste National Park. Scientists focused in part on parasitoid wasps, a highly diverse group known for laying eggs inside other insects.
By comparing different survey methods, including trap data and analysis of parasitized caterpillars, researchers found limited overlap in identified species, suggesting that even intensive sampling captures only a fraction of local diversity.
Using statistical techniques originally developed in epidemiology to estimate hidden populations, the team calculated that the park alone could contain more than 300,000 insect species — far more than previously recorded.
They then scaled the estimate globally using biodiversity comparisons with tree species, concluding that Earth may host between 13 million and nearly 25 million insect species, with a midpoint estimate of about 20 million.
Brian Fisher, a curator of entomology at the California Academy of Sciences, said the estimate highlights how current figures likely underestimate insect diversity, and added that the precise total remains uncertain.
Researchers said the estimate highlights the scale of undiscovered biodiversity and underscores conservation challenges, particularly as many insect species are believed to be declining due to habitat loss, climate change and other environmental pressures.
Experts say the findings suggest that large portions of Earth’s insect life remain unknown and may potentially be unrecorded before they disappear.
