Common Harvestman (Phalangium opilio): Daddy Longlegs Facts

What is a harvestman?

Harvestmen are arachnids, the same class as spiders, scorpions, ticks and mites, but they form their own order, Opiliones. Scientists have described more than 6,600 species worldwide, and the true number may be over 10,000. They live on every continent except Antarctica. Harvestmen are an ancient group: fossils from the Rhynie chert of Scotland, about 400 million years old, already look much like the species alive today.

The common harvestman belongs to the suborder Eupnoi, the classic long-legged harvestmen. Because it is so common and so widely spread, biologists use it as a model species for the whole order. A draft of its genome was published in 2021, and laboratory colonies are used to study how arachnid legs and eyes develop.

Harvestman vs spider: how to tell them apart

The quickest clue is the body. A spider has two clear body parts joined by a narrow waist (the pedicel). In a harvestman the front part (cephalothorax) and the abdomen are joined along their full width, so the body looks like a single oval bead hanging between the legs.

Other differences are easy to remember:

In some homes the name “daddy longlegs” also refers to the cellar spider, a real spider that hangs in messy webs in corners, and in Britain and Ireland it usually means the crane fly, an insect with wings. You can learn more in are daddy longlegs venomous? and in our guide to spiders vs insects.

Appearance and size

Adult common harvestmen have a body length of about 3.5–9 mm (1/8–3/8 in), and females are usually larger-bodied than males. The legs are many times longer than the body, so even a small individual can span several centimeters. Like all arachnids it has eight legs. Each leg ends in a flexible section split into many tiny segments, which lets the harvestman wrap the tip around twigs and grass stems like a whip.

The body is light brown to grayish above, often with a darker saddle-shaped pattern, and pale cream underneath. The two eyes sit on a small raised bump called the ocularium, in the middle of the back, facing sideways. Studies of developing embryos in this species have shown that harvestmen also carry two extra pairs of tiny vestigial eyes, which do not form working eyes in adults.

Males are easy to recognize up close. Their mouthparts (chelicerae) carry long, forward-pointing horn-like projections, and their pedipalps, the small leg-like limbs near the mouth, are longer than the female’s. Males use these structures when they compete with each other. A similar European species, Mitopus morio, looks much alike, and experts separate the two by small details of the front of the body.

Habitat and range

The common harvestman is native to Europe, northern and central Asia and Asia Minor. People carried it to North America, North Africa and New Zealand. In North America it is now common in southern Canada and across most of the United States outside the deserts.

It prefers open, sunny and fairly dry places rather than deep forest. Typical habitats include meadows, field margins, hedgerows, gardens, lawns, quarries and city green spaces. It is also common in farmland among crops such as corn, alfalfa, cereals, potatoes and cabbage. During the day it often rests on vertical surfaces such as tree trunks, fences and walls, with a liking for wood, which holds warmth and moisture well.

What do common harvestmen eat?

The common harvestman is a generalist predator and scavenger. It hunts small, soft-bodied animals, especially aphids, caterpillars, leafhoppers, beetle larvae and mites, and it also feeds on the eggs of moths. It readily eats dead insects and sometimes other harvestmen. Harvestmen as a group are unusual arachnids because many species also eat fungi, fruit, bird droppings and other plant or animal scraps.

Unlike spiders, harvestmen can swallow small solid pieces of food. They tear their meal apart with small pincer-like chelicerae and pass the pieces to a mouth formed between the bases of the front limbs. Because the long legs need to stay clean for sensing, a harvestman pulls each leg through its mouthparts to groom it after feeding. Read more in what do daddy longlegs eat?.

In farmland this habit makes the common harvestman a useful ally. It cannot control pest outbreaks on its own, but together with spiders, ground beetles and other predators it helps keep aphids and caterpillars in check.

Behavior and defenses

The common harvestman is mainly nocturnal. In field studies most of its activity happens between dusk and dawn, when it walks through vegetation and taps the ground and plants with its long second pair of legs. These legs work like an insect’s antennae, because the harvestman’s simple eyes probably cannot form sharp images.

Harvestmen have several ways to avoid being eaten. They have a pair of scent glands near the front of the body that release a strong-smelling fluid when disturbed, which makes them taste unpleasant to many predators. Long-legged species may bob their bodies up and down rapidly to confuse an attacker. They can also run quickly on their long legs or drop from plants and stay still.

The most famous defense is autotomy, the ability to shed a leg. If a bird, spider or ant grabs a leg, the harvestman can break it off and escape. The detached leg keeps twitching for a while, which can hold the predator’s attention. The cost is permanent, because adult harvestmen do not regrow lost legs. Our article why do daddy longlegs lose their legs? explains how this works.

Many harvestmen also gather in groups in sheltered, damp places, where the combined scent of many individuals may help protect them. This is less obvious in the common harvestman, which is usually seen on its own.

Reproduction and life cycle

Harvestmen mate in a way unusual among arachnids. Male spiders and scorpions pass sperm indirectly, but most male harvestmen have a penis and mate directly with the female. In the common harvestman, mating can happen within seconds of a male and female meeting, and both sexes mate with several partners.

The female uses a long egg-laying tube (ovipositor) to place her eggs in moist soil, moss or crevices. Each egg is tiny, about 0.55 mm across, and they are laid in clusters ranging from a handful to several hundred. Development depends on temperature. In warm conditions, eggs can hatch and the young can reach adulthood within a few months, while cold weather slows or pauses growth.

The young look like small, short-legged adults. In studies of North American populations, they passed through a short non-feeding stage and then six juvenile stages (instars), molting each time before becoming adults. Adult males develop their cheliceral horns only near the end of this process.

How long do common harvestmen live?

The common harvestman lives for less than a year in most places. In much of Europe it has one generation per year: it spends the winter as eggs, the young grow in spring, and adults appear from early summer into autumn. In some warmer parts of North America there may be two or three generations a year. Adults in laboratory studies lived for about 40–60 days, and in the wild many are eaten or killed by frost before that.

Predators and conservation status

Common harvestmen are eaten by birds, frogs and toads, lizards, shrews, spiders, ground beetles and other invertebrates. Some parasites, including red mite larvae, often cling to their legs and bodies. Broad-spectrum insecticides harm them too, which matters on farms where they are valued as pest predators.

The species has not been assessed by the IUCN Red List, so its status is Not Evaluated. It is widespread, abundant and thrives in places changed by people, so it is not considered at risk. A small number of other harvestmen, especially cave species in Brazil and central Texas, are rare and legally protected.

Myths and relationship with people

The best-known myth claims that daddy longlegs are the most venomous animals in the world but cannot bite through human skin. For harvestmen this is false on both counts: they have no venom at all, and their tiny mouthparts are made for tearing food. They are completely harmless to people.

Another common belief is that harvestmen are spiders. They are distant relatives within the arachnids, but they belong to a separate order, much as scorpions or ticks do. To see how many real spiders use venom, read are all spiders venomous?.

For most people, the common harvestman is a quiet garden neighbor that appears on walls and window frames in late summer. It does not build webs, damage homes or spread disease, and it eats small insects and dead material, so it is best left alone.