Zebra (Salticus scenicus)

Physical description and identification

The zebra spider is one of the easiest spiders in the northern hemisphere to name on sight. It is small, boldly barred black and white, and moves in a jerky stop-start rhythm across sunlit brick, stone and timber, swivelling its whole body to look at anything that moves. The pattern is made of white hairs over a dark cuticle, so a worn individual late in the season looks greyer than a freshly moulted one.

Adults

• Size: females measure about 5–9 mm in body length, most often 5–7 mm, and males about 5–6 mm. Both are small enough to sit comfortably on a fingernail.
• Colour and pattern: black to dark grey-brown, with a white band across the front of the abdomen and two or three further white bars or chevrons behind it, plus pale streaks along the sides of the carapace. The legs are banded light and dark.
• Males: darker and slimmer, and immediately recognisable by their chelicerae, which are enlarged and project forwards and outwards. They are used in ritual contests with rival males and to hold the female during mating. No other common European jumping spider of this size has jaws like them.
• Females: plumper and often paler, with broader, cleaner white banding and normal, unenlarged jaws.
• Eyes: two great dark headlamps at the front, a smaller pair immediately outside them, and four small eyes set back along the edges of the head. The big pair see detail; the rest report motion from almost every direction, which is why a zebra spider notices a hand long before you expect it to. Our guide to spider eyes sets out the full arrangement.

Eggs and egg sac

The female spins a closed silk cell in a dry, sheltered place — under a stone, behind flaking bark, in a mortar joint or under a window ledge — and lays her eggs there inside a white sac. She remains in the cell guarding the sac, and does not abandon the brood at hatching.

Spiderlings

The young hatch as pale miniatures of the adults and stay with the mother inside the cell until their second moult, after which they disperse and begin hunting for themselves. They pass their first winter as part-grown juveniles in sealed silk cells and mature the following spring, males usually a little before females. Growth happens in stages, and every one of them is completed out of sight in a freshly built silk retreat — see our guide to spider molting.

Hunting, not a web

Zebra spiders build no capture web. Silk is used for the retreat, for the egg sac and for the dragline that the spider attaches before every leap; the line saves it if the jump misses and also steers the body in flight. The hunt is pure vision. Movement is picked up by the side eyes, the spider turns to bring the principal eyes on target, then stalks in short bursts, freezing whenever the prey looks up and sometimes detouring around an obstacle to reach a better launch point. At the end it crouches, fixes the dragline and straightens its third and fourth legs explosively — a launch driven by leg muscle together with a surge of internal fluid pressure, because those joints have no extensor muscles at all. For spiders that build traps instead, see our guide to spider webs.

Where zebra spiders live

Salticus scenicus is a Holarctic species, found right across the temperate northern hemisphere. It is abundant throughout Britain and Ireland, continental Europe and northern Asia, and occurs across much of northern North America, including the northern United States and southern Canada. It is one of the best known and most photographed spiders in the UK.

The habitat is a warm, hard, sunlit surface with crevices behind it: house and garden walls, fences, rocks, quarry faces, tree trunks, greenhouse frames, sheds and paving. The spider is strongly sun-loving — absent on a cool morning, out within half an hour of sunshine. It also comes indoors, hunting flies on window sills and along the folds of curtains, which is why it appears on lists of common house spiders even though it belongs outdoors.

Are zebra spiders venomous?

Yes, in the way that nearly all spiders are venomous: the zebra spider injects a tiny amount of venom to immobilise the flies and midges it catches. It is of no medical significance to people or pets. Nothing in the family Salticidae presents a hazard to humans, no antivenom exists for the group and none is needed, and no serious reaction has ever been documented from a zebra spider bite anywhere in its enormous range.

Can zebra spiders bite?

In practice, almost never. The zebra spider is a few millimetres long with correspondingly tiny fangs, and its reflex on meeting something as large as a hand is to jump clear on its dragline. For a bite to happen the spider has to be squeezed or pinned, and even then its chelicerae often cannot penetrate human skin.

On the rare occasion a bite does register it feels like a faint pinprick, may leave a small red mark, and fades within hours with no aftereffects. Wash the area with soap and water and leave it alone; no cream or medical visit is needed. The only reason to see a doctor would be an unusual allergic response — spreading hives, or breathing difficulty — which is a reaction to the proteins rather than a toxic effect of the venom.

Ecological importance and behavior of the zebra spider

The zebra spider is a solitary daytime hunter with an unusually flexible approach to prey, taking insects close to its own size and readily tackling other jumping spiders. Studies of salticid hunting show these spiders planning detours — leaving sight of the target, travelling a roundabout route and arriving at a chosen launch point — remarkable navigation for a brain the size of a poppy seed.

Courtship: the male performs a zig-zag dance in front of the female, raising and waving his front legs, jerking his abdomen and shifting sideways while he closes the distance. She judges the display before allowing contact, and he uses his enlarged jaws to hold her during mating. Females that are not receptive drive males off, and an unlucky suitor may be treated as prey.

Natural predators: spider-hunting wasps of the family Pompilidae are important specialists, paralysing salticids to provision their nests, and mantises take them in warmer parts of the range. Birds, lizards, ants and larger spiders prey on them too, and speed and unpredictable jumping are the main defence.

Seasonal behaviour: adults are most conspicuous from May to September, with courtship concentrated in late spring. Juveniles overwinter in sealed silk cells under bark, stones and window ledges. Individuals generally live about a year, sometimes longer in the shelter of a building.

Relationship with humans: the zebra spider is harmless, and one of the very few spiders that clearly notices a person — it turns to face you and often lifts the front of its body to look. It is a spider, not an insect, a point frequently garbled online. Its habit of hunting flies on window sills makes it a welcome resident.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The genus name Salticus comes from the Latin for leaping and dancing, and scenicus from a word meaning theatrical — a double reference to the male's courtship dance and the spider's stagey black-and-white costume.
• The species was named by Carl Clerck in 1757, in the first work of zoology ever to use consistent binomial names for animals.
• Behind each of the big front eyes sits a narrow, stacked retina on a muscular stalk, scanning the image like a searchlight. Nothing else this small sees so well, and jumping spiders see in colour too.
• Salticids are among the very few invertebrates known to plan a detour: shown a target and then made to lose sight of it, they travel a roundabout route and arrive where the prey should be.
• Because the leap depends on a surge of body fluid, a dehydrated or freshly moulted zebra spider cannot jump properly and has to walk until its internal pressure recovers.

In summary, the zebra spider is a harmless, sharp-eyed little hunter with the best eyesight of any animal its size and no capture web at all. Learn the white bars and the alert, stop-start walk and you will start seeing it on every sunny wall you pass.