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Spiders may seem unsettling, but their presence is pervasive—almost always lurking nearby. While their appearance can be unnerving, the real marvel lies in the sheer volume of prey they consume each year. According to a 2017 study in The Science of Nature, the global spider community kills between 400 and 800 million metric tons of insects annually—a figure that eclipses the combined biomass of many large marine predators.

These numbers highlight not only the ecological importance of spiders as natural pest controllers but also give us a glimpse into their sheer abundance and hunting efficiency. The study’s authors estimate the world’s total spider biomass at roughly 25 million metric tons, and from this figure—combined with feeding rates and web‑density data—they arrive at the 400–800‑million‑ton range.

Spiders eat more weight annually than the entire human population of Earth

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The scale is staggering. Humans worldwide consume about 400 million metric tons of meat and fish each year, while the global seabird population is estimated to kill 70 million metric tons of prey annually. In contrast, spiders may consume up to 12 times that amount. Even more striking: the total mass of the human population—roughly 390 million metric tons—is less than the annual prey biomass eaten by spiders.

What do spiders actually eat?

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Spiders target a limited set of arthropods, primarily from the orders Diptera, Hemiptera, Hymenoptera, Collembola, Coleoptera, Lepidoptera, Orthoptera, and even Araneae—meaning they occasionally prey on other spiders. In warmer climates and among actively hunting species, spider predation on conspecifics is more common than in colder regions or among web‑spinners.

Beyond insects, some arachnids also consume earthworms, slugs, snails, and, rarely, small vertebrates such as frogs, snakes, and lizards. The Goliath birdeater—world’s largest spider by mass—has occasionally been recorded feeding on birds, but such events are exceptional. Overall, spiders’ broad dietary range contributes to their massive annual prey kill.

Importantly, forest and grassland spiders account for over 95% of the global prey consumption, underscoring that most of the insects affected by spiders live outside human dwellings. This natural pest‑control service is vital for maintaining ecological balance and limiting disease‑carrying pests in natural habitats.