Harvestmen are not spiders, and they certainly are not the world's most venomous creatures.

Nature · Published 29 September 2026 Swipe more like this →

In short: Often mistaken for spiders, harvestmen are a distinct order of arachnids that lack both venom glands and silk. Despite an urban legend claiming they are the most venomous animals on Earth, these harmless creatures cannot even break human skin. Their true survival strategy involves complex chemical defenses and remarkable evolutionary adaptations.

The Opiliones, or harvestmen, represent a distinct evolutionary lineage within the Arachnida. Unlike spiders, which possess a constricted waist separating their abdomen from their cephalothorax, harvestmen have a broad connection that gives them a single, oval-shaped body. Their internal anatomy is equally distinct; they lack the sucking stomachs found in other arachnids, allowing them to ingest solid food particles instead of just liquids. This unique feeding apparatus, the stomotheca, makes them vulnerable to internal parasites like gregarines, yet it grants them a diverse diet that includes fungi, plant material, and dead organisms.

Their survival strategies are remarkably sophisticated. Many species utilize chemical warfare, secreting noxious fluids from scent glands called ozopores to deter predators. Others employ autotomy, the voluntary amputation of a limb when captured. These detached legs can twitch for up to an hour, powered by internal 'pacemakers' in the femur, serving as a distraction while the harvestman escapes. While some species rely on crypsis or mimicry to avoid detection, others use aggressive defense, such as the armored Laniatores, which can use their pedipalps to pinch and injure attackers.

Despite their ancient history—with fossils appearing in 400-million-year-old Scottish rocks—harvestmen remain a scientifically neglected group. Much of our systematic knowledge stems from the work of Carl Friedrich Roewer, who described roughly 2,260 species between the 1910s and 1950s. Today, over 6,650 species are known, though estimates suggest the true number may exceed 10,000. Many of these species, particularly those restricted to caves in Brazil, the United States, and the Canary Islands, face significant threats from habitat destruction, highlighting the urgent need for further study of these misunderstood arachnids.

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