Portia Labiata

Physical description and identification

Portia labiata is the most widespread member of Portia, a genus of jumping spiders that specialises in eating other spiders. Nothing about its appearance is showy. It is a drab, hairy, slow-moving spider whose whole design is aimed at not looking like a spider at all — from a short distance it reads as a curl of dead leaf or a scrap of debris snagged in silk.

Adults

• Size: females measure 7–10 mm in body length, with a carapace of about 2.8–3.8 mm; males are smaller at 5–7.5 mm with a carapace of 2.4–3.0 mm. Females are noticeably heavier as well as longer.
• Colour: orange-brown across the front of the body and darker, often nearly black, towards the rear. The female's abdomen is mottled black and brown; the male's is brown with lighter markings. Both sexes have dark brown legs with pale flecks on the femora, and pale hairs around the front of the face that give the species its "white-moustached" nickname.
• Eyes: eight eyes in the salticid pattern, dominated by a large forward-facing pair. Their field of view is narrow, so the spider works through a scene piece by piece, but within that narrow window the resolution is exceptional for an animal of this size. See our guide to spider eyes for how the arrangement works.
• Distinctive features: fringes and tufts of hair on the legs, carapace and abdomen, and a slow, stilting walk with long freezes between steps. Combined, they make a moving P. labiata look like wind-stirred detritus rather than an approaching predator.

Eggs

The female lays her eggs on a dead leaf and covers them with a sheet of silk. Where dead leaves are scarce she spins a small silk platform and uses that instead. Clutches are small by spider standards, and the female remains nearby rather than abandoning the eggs.

Spiderlings

Hatchlings stay in or beside the mother's retreat for a short period, then disperse to establish their own territories. They hunt spiders from an early age: the elaborate behaviour of the species is largely built in rather than learned from an adult, and experience sharpens it rather than creating it.

The web and hunting

Unlike most jumping spiders, P. labiata spins its own capture web — a small, irregular structure that catches insects — and frequently attaches it to the web of a neighbouring spider so that the two become one continuous surface it can cross. See our guide to spider webs for how that differs from an orb or a sheet.

What it does on that surface is the reason the species is famous. Perched on the silk, it plucks, taps and shakes with its legs, palps and abdomen, producing vibrations that imitate a trapped insect or a courting male. If one pattern brings no response it tries another, then another, retaining whatever draws the resident closer — a genuine trial-and-error search rather than a single fixed signal. Where the web cannot be entered safely it will instead take a detour, following a route across leaves and stems that leads away from the prey and out of sight of it for up to an hour before arriving above the target.

Where Portia labiata lives

The species ranges across South and Southeast Asia. Records run from Sri Lanka and southern India through Myanmar, Thailand and southern China to Malaysia, Singapore, Sumatra and Java in Indonesia, and the Philippines, where the population around Los Baños on Luzon has been studied in unusual depth. Older lists that repeat Burma twice are simply duplicating the same country under two names.

Habitat is damp and structurally complex: rainforest, secondary regrowth, riverbank vegetation, plantation edges and overgrown gardens. What matters is not the plant species but the density of other spiders, because those are the prey. For that reason P. labiata is also common on the outside walls, eaves and porches of buildings within its range, where webs accumulate around lights. Anyone looking for one should search other spiders' webs rather than foliage.

Is Portia labiata venomous?

Yes, in the sense that applies to nearly every spider. P. labiata uses venom to subdue prey, and because that prey is usually another spider the venom works quickly on arachnids. It carries no medical significance for people or pets. No antivenom exists, because none has ever been needed, and no serious reaction to a bite from this species has been documented. It is unrelated to the widow, recluse and funnel-web groups that cause real harm.

Can Portia labiata bite?

It can, but it effectively never does. This is a spider whose survival depends on going unnoticed; confronted with something as large as a hand it freezes, then edges away or drops on a dragline. Bites on people are rare enough to be absent from the clinical literature, and the expected result would be a pinprick and a small red mark that fades within a few hours. Wash the site with soap and water, apply a cold pack if it is sore, and seek advice only if redness spreads over the following days — that indicates infection, not venom.

Ecological importance and behavior of Portia labiata

P. labiata is a predator of predators. Its diet is built around other spiders — web-builders of many families, other jumping spiders, and spider eggs — with insects taken when convenient. Because it kills animals that are themselves major insect predators, it sits unusually high in the invertebrate food web for something that weighs a fraction of a gram, and it helps shape which spiders can hold territory in a patch of vegetation.

Flexible tactics: the species does not use one routine. Against a web-bound spider it mimics; against a wandering hunter it stalks in the open behind its cryptic outline; against a spitting spider carrying an egg sac it circles and attacks from behind, out of range of the gum the prey can spray. The Philippine population is particularly associated with hunting spitting spiders, and shows a clear preference for females that are carrying eggs and therefore handicapped.

Learning and prey choice: laboratory work has shown P. labiata selecting the correct detour route before setting out, persisting on it after the prey passes from view, and responding to experimental situations in ways that suggest it holds an expectation about what it should find. Females tend to favour smaller, safer prey items over large ones, which makes sense for a predator whose meals can fight back.

Natural predators: frogs, lizards, birds, mantises, assassin bugs, ants and larger spiders all take P. labiata, and wandering males are the most exposed. Ants are a particular hazard, and the spider avoids ant-heavy foliage rather than confronting them. Camouflage and stillness are its main defences.

Life cycle: individuals live roughly a year to eighteen months, females longer than males. In the wet tropics adults occur all year, with peaks following rain. Courting males drum and wave in front of the female's principal eyes, and a misjudged approach can end with the male being eaten.

Relationship with humans: harmless and useful. Around buildings it quietly reduces the number of web spiders on walls and porches, and in science it has done more than any other invertebrate to change what researchers believe a small brain can do.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The Los Baños population in the Philippines is known for preying on spitting spiders, approaching from behind where the spit cannot reach and favouring females encumbered by an egg sac.
• An older claim that Philippine Portia labiata are eaten by ants rather than eating them garbles the real picture: ants are a hazard this spider avoids, and its specialisation is on other spiders, not on ants.
• The species appears in Adrian Tchaikovsky's novel Children of Time, where a lineage of uplifted Portia labiata carries the story — a rare case of a spider chosen for fiction because of published science rather than in spite of it.
• Its hunting looks unhurried to the point of laziness. That is deliberate: fast movement is what a web spider detects, so the entire approach is built around moving slowly enough to read as debris.

In summary, Portia labiata is a small, drab Asian jumping spider that hunts other spiders by deception and persistence. It is completely harmless to people, valuable around houses, and the single best demonstration that a brain the size of a pinhead can still solve a problem it has never met before.