For four decades, the scientific consensus placed the number of insect species on Earth at about 6 million. A new study based on massive genetic sampling in Costa Rica revises this estimate to between 14 and 20 million — two to three times what was previously thought. And only 1.2 million species have been described so far.
What you will learn
- How researchers used parasitoid wasps and genetic barcodes to recalibrate the total number of insects
- Why a 169,000-hectare national park in Costa Rica served as a laboratory for extrapolating to a global scale
- What this massive revision means for the insect apocalypse crisis
A 40-year consensus challenged
For four decades, the scientific community agreed on an estimate of roughly 6 million insect species worldwide. A new study published in the Proceedings of the National Academy of Sciences upends this figure: by leveraging genetic data from 1.6 million tropical insects, researchers now estimate the total number of species to be between 14 and 20 million — essentially doubling or tripling the previous estimate.
To date, only about 1.2 million insect species have been formally described by science — named and characterized sufficiently to enable identification. The vast majority would therefore remain unknown.
Costa Rica as an extrapolation laboratory
To arrive at this estimate, the team exploited an intensive sampling conducted in the Área de Conservación Guanacaste, a protected area of 169,000 hectares in northwestern Costa Rica. Their method focused on Microgastrinae, an incredibly diverse subfamily of small parasitoid wasps that lay their eggs inside caterpillars.
Fifteen Malaise traps — tents designed to capture flying insects — allowed the capture of more than 1.6 million insects, all identified by genetic barcodes: a rapid DNA sequencing technique that enables species identification without full taxonomic analyses. These traps logged nearly 54,000 insect species in this area, including 1,414 distinct Microgastrinae wasp species.
From local ratio to global total
The team then calculated the ratio between the wasps actually detected and the number of species estimated to be undetected, applying this same ratio to the 54,000 insects recorded to estimate roughly 333,000 insect species present in this single protected area.
To extrapolate globally, the researchers computed the ratio between the estimated number of tree species worldwide (around 73,000) and those present in the studied Costa Rican area (1,200 to 1,500), a method also validated with mammals, amphibians, and Saturniid moths. By applying this ratio to the 333,000 local insect species, the global estimate yielded a range of 14 to 20 million species.
A risk of silent extinction
This massive revision takes on a troubling dimension in the context of what some reports call the “insect apocalypse” — a widespread decline in insect populations linked to human activity. According to Laura Melissa Guzman, the study’s lead author, the large number of undescribed insects raises a specific concern: many species might already be in decline, or even extinct, without having yet been discovered by science.
This ignorance represents a direct obstacle to conservation efforts. As Guzman summarizes, you cannot protect species whose existence is unknown — making this revised estimate not merely a scientific curiosity, but a concrete challenge for the protection of global biodiversity.
