Tan Jumping (Platycryptus undatus)
Flattened like a coin and patterned in grey, tan and cream, the tan jumping spider spends its life pressed to bark, fence boards and porch siding across eastern North America. It builds no snare, stalks its prey on foot in daylight, and is famous among naturalists for calmly walking onto an offered finger.
By Dr. James WatuwaPublished May 10, 2019Updated September 13, 2026✓ Reviewed by Dr Richard J. Pearce (PhD)
In this guide
Physical description and identification
The tan jumping spider is built for life on flat surfaces. Where most jumping spiders stand tall, this one is flattened from top to bottom, so it can press itself into a bark fissure or a gap behind a shutter and effectively disappear. Colored in mottled grey, tan and brown with cream markings, it is genuinely hard to see until it moves.
Adults
- Size: females measure about 10–13 mm (0.39–0.51 in) in body length, males about 8.5–9.5 mm (0.33–0.37 in). Legs are moderately long and held out to the sides, which adds to the low, flat silhouette.
- Color: a base of brown, tan or grey, speckled with black and white scales. The abdomen carries a series of pale, wavy transverse bands or chevrons that run from front to back — the feature behind the species name undatus, meaning "wavy". Many individuals show reddish or orange scales on the face around the main eyes, and the body is covered in short flattened hairs that catch the light.
- Shape: the whole body is dorsoventrally compressed — flattened top to bottom, not side to side — which lets the spider slip into crevices far too narrow for a bulkier salticid.
- Eyes: eight eyes in four pairs across three rows on a wide, blunt face. The two anterior median eyes are large and forward-facing and provide the sharp, color-capable vision the family is known for; the smaller lateral eyes are set far back along the sides, giving motion detection over close to a full circle. Our guide to spider eyes explains how the four pairs work together.
- Sexes: males are smaller and usually darker, with noticeably enlarged chelicerae and swollen pedipalps; females are broader across the abdomen and paler.
Eggs and egg sac
Eggs are laid in summer inside a flat silk retreat, most often under loose bark, in a split fence rail, behind siding or under a windowsill. The female seals the sac into the retreat and remains with it. Spiderlings hatch roughly three to four weeks later.
Spiderlings
The young stay in the maternal retreat through the first molt, then disperse over the same vertical surfaces the adults use. They pass the winter as part-grown juveniles inside dense silk retreats and complete their growth the following spring through a series of molts. Several individuals are sometimes found overwintering under the same slab of bark, each in its own silk pocket.
The web and how it hunts
Tan jumping spiders build no capture web. Silk goes into a flattened, tent-like retreat used for sleeping, molting, overwintering and egg-laying, and into a dragline anchored before each jump. Hunting is done on foot and by sight during the day: the spider detects movement with its side eyes, swings around to inspect the target with its main eyes, creeps within range, then extends its rear legs by a sudden surge of internal fluid pressure — a hydraulic launch rather than a muscular one — and lands on the prey. If it misses, the dragline catches it. For how this differs from snare-building species, see our guide to spider webs.
Where tan jumping spiders live
Platycryptus undatus is an eastern North American species. It ranges from southern Canada — southern Ontario, Quebec and the Maritimes — south through the eastern United States to Florida and west to the eastern Great Plains and Texas, continuing into parts of Mexico. Its western counterpart, Platycryptus californicus, replaces it on the Pacific side of the continent.
The habitat is vertical and flat. Look on tree trunks — especially rough-barked oaks, maples and pines — and on fence posts, wooden rails, garden walls, deck boards, window frames, porch columns and outbuildings. It is one of the jumping spiders most often noticed by people precisely because it lives on the surfaces we walk past daily. Indoors it turns up occasionally around window frames in autumn, hunting the flies that gather there.
Are tan jumping spiders venomous?
Yes, in the ordinary way that nearly all spiders are: venom is injected through the fangs to immobilise insects. It is not medically significant to humans, pets or livestock. The tan jumping spider has none of the tissue-damaging enzymes of the recluse spiders or the potent neurotoxin of the widows, and no jumping spider is known to have caused serious envenomation.
Can tan jumping spiders bite?
They can, but they very rarely do. This is one of the most placid spiders a person is likely to meet: rather than fleeing, a tan jumper often turns to watch, and many will step calmly onto an offered hand. A bite requires the spider to be squeezed or trapped against skin, and it produces no more than a brief pinch and perhaps a faint red mark that fades within a few hours. Wash the area with soap and water, apply a cold pack if it feels sore, and seek medical advice only if swelling spreads well beyond the site, if hives or breathing difficulty develop, which indicates an allergic reaction rather than the venom itself, or if the wound later looks infected.
Not a recluse: a flat brown spider on a wall alarms people who have heard of recluses. A brown recluse has six eyes in three pairs, long smooth legs, a uniform tan body with a violin mark and no pattern on the abdomen. A tan jumper has eight eyes including two huge forward-facing ones, short hairy legs, and clear wavy pale bands across the abdomen.
Ecological importance and behavior of the tan jumping spider
Tan jumpers are diurnal visual hunters. They take flies, moths and their caterpillars, leafhoppers, small beetles, ants, true bugs and other spiders, and because they patrol trunks and walls they intercept insects that no aerial web would catch. On a tree with a heavy bark-insect population several adults may hold overlapping territories on the same trunk.
Camouflage and defence: the flattened body, mottled scales and wavy pattern make the spider almost invisible when it sits still on bark. Its first response to a threat is usually to sidle around to the far side of the trunk, crab-fashion, rather than to jump away.
Courtship: the male's display is visual — front legs raised and waved, body rocking, his enlarged chelicerae angled toward the female. He advances only while she holds still.
Natural predators: insect-eating birds such as nuthatches, woodpeckers and warblers, along with lizards, mantises, spider-hunting and mud-dauber wasps, and larger spiders. Parasitic wasps and ants attack the egg sacs.
Seasonal pattern: adults are most visible from late spring through autumn; juveniles overwinter under bark and mature in spring. Most individuals live around a year.
Relationship with humans: entirely benign, and arguably the best ambassador its family has. It removes pest insects from trees and buildings, needs no control measures, and its calm curiosity has introduced a great many people to spiders they would otherwise have feared.
Similar spiders and how to tell them apart
| Spider | How it differs from the tan jumping spider |
|---|---|
| Other Platycryptus species | Very similar in shape and habits. P. californicus replaces P. undatus in western North America, so geography usually settles the identification. |
| Gray wall jumping spider (Menemerus bivittatus) | Also flat and pale, but with dark lateral stripes along the carapace and a fringe of white hairs; a warm-climate, mostly urban species. |
| Bold jumping spider (Phidippus audax) | Bulky and tall rather than flat, glossy black with a white triangle and iridescent green jaws, and typically on vegetation or open sunlit walls. |
| Zebra jumping spider (Salticus scenicus) | Much smaller at 5–7 mm and boldly striped black and white rather than mottled grey-tan. |
| Brown recluse | Six eyes in three pairs, long thin smooth legs, a violin mark and a plain abdomen. Medically significant, hides in dark interior clutter, and never hunts in the open by day. |
Quick facts
| Distribution | Eastern North America from southern Canada to Florida and Texas, extending into Mexico |
|---|---|
| Habitat | Vertical surfaces: tree trunks, fence posts, rails, walls, deck boards, window frames and outbuildings |
| Diet | Flies, moths and caterpillars, leafhoppers, true bugs, ants, small beetles and other spiders |
| Lifespan | About one year |
| Predators | Bark-foraging birds, lizards, mantises, spider and mud-dauber wasps, larger spiders |
| Silk use | Flat retreat for sleeping, molting, overwintering and eggs, plus a safety dragline |
| Eggs | Laid in summer inside the retreat; spiderlings hatch in about three to four weeks |
| IUCN status | Not evaluated; common throughout its range |
Did you know?
- The name undatus is Latin for "wavy", after the undulating pale bands across the abdomen; Platycryptus means roughly "flat and hidden".
- Between them the four pairs of eyes cover close to a full circle, so the spider can register movement behind it and then swing around to look properly with its big front pair.
- The flattened body is not just camouflage — it lets the spider occupy crevices narrow enough to exclude most of its predators.
- Tan jumpers frequently overwinter communally under a single sheet of loose bark, each individual sealed in its own silk pocket.
- They are among the few wild spiders that will walk onto a person's hand without being coaxed, which is why they turn up so often in nature-education programmes.
In summary, the tan jumping spider is a flat, cryptically patterned, entirely harmless hunter of bark and boards. Learn the wavy abdominal bands and the two big forward eyes and you will spot it on every fence post you pass.
Frequently asked questions about the tan jumping spider
How big do tan jumping spiders get?
Adult females measure about 10–13 mm (0.39–0.51 in) in body length and males about 8.5–9.5 mm (0.33–0.37 in). The body is flattened from top to bottom rather than rounded, which makes the spider look larger and lower than its measurements suggest.
What does a tan jumping spider look like?
It is a flat, mottled spider in brown, tan and grey, speckled with black and white scales, with a series of pale wavy bands across the abdomen and often reddish scales around the front eyes. Two large forward-facing eyes sit on a wide, blunt face.
Why is the tan jumping spider so flat?
The body is compressed from top to bottom so the spider can push into narrow bark fissures, gaps behind siding and splits in fence rails. That gives it both a hiding place and a nest site in crevices too tight for most of its predators to follow.
Do tan jumping spiders build webs?
Not for catching prey. They spin a flattened silk retreat for sleeping, molting, overwintering and egg-laying, and they anchor a dragline before each jump. Prey is taken by stalking and pouncing in daylight, using vision rather than a snare.
Are tan jumping spiders venomous to humans?
They carry venom for subduing insects, but it is not medically significant to people or pets. The species lacks the tissue-damaging enzymes of recluse spiders and the neurotoxin of widows, and no jumping spider has been shown to cause serious envenomation.
Do tan jumping spiders bite people?
Very rarely. They are unusually calm around humans and will often step onto an offered hand rather than flee. A bite requires the spider to be squeezed or trapped against skin, and it feels like a brief pinch with at most a faint red mark that fades in hours.
Where do tan jumping spiders lay their eggs?
In summer, inside a flat silk retreat tucked under loose bark, in a split fence rail, behind siding or under a windowsill. The female stays with the sealed sac, and the spiderlings hatch roughly three to four weeks later and remain in the retreat through their first molt.
Where do tan jumping spiders live?
Across eastern North America, from southern Canada south to Florida and west to the eastern Great Plains, Texas and parts of Mexico. They live on vertical surfaces: tree trunks, fence posts, rails, garden walls, deck boards, window frames and outbuildings.
Can tan jumping spiders really see all around them?
Close to it. The four pairs of eyes together cover almost a full circle, with the rear-set lateral eyes detecting movement behind the spider. Detail and color come only from the two huge front eyes, which is why the spider turns its whole body to inspect something.
Are tan jumping spiders good to have around the house?
Yes. They hunt flies, moths, caterpillars, leafhoppers and other insects on walls, fences and trees, damage nothing, and pose no risk to people or pets. If one wanders indoors, cup it and release it on an outside wall or tree trunk.
References
- World Spider Catalog (2026). Platycryptus undatus (De Geer, 1778). Natural History Museum Bern. wsc.nmbe.ch/spec-data/38667/taxon
