Cardinal Jumping (Phidippus cardinalis)

Physical description and identification

The cardinal jumping spider is hard to mistake once you have seen it. The whole upper surface — carapace and abdomen alike — is covered in dense scales of saturated orange-red to scarlet, while the legs and underside are black and conspicuously hairy. The scheme is not accidental: it belongs to the velvet ants, and the spider is borrowing it.

Adults

• Size: females are roughly 10–13 mm (0.4–0.5 in) in body length and males a little smaller at about 7–10 mm. Both sexes look larger than they are because the legs are long and thickly clothed in setae.
• Color: bright red to red-orange scales over the carapace and the dorsal abdomen, with glossy black legs, black sides and a black underside. Many individuals show a pair of narrow dark bands or a dark margin toward the rear of the abdomen. The red fades to a duller brick tone in worn individuals and is brightest just after a moult.
• Eyes: eight eyes in four pairs on a high, squared carapace. The two huge anterior median eyes face directly forward and give the spider its remarkable acuity; the smaller side and rear pairs cover nearly the whole horizon for movement. This layout is the fastest way to rule out a red crab spider or a young wolf spider — our guide to spider eyes sets out the pattern.
• Distinctive features: the chelicerae are iridescent, usually flashing green or blue-violet against the red body, a hallmark of the genus Phidippus. Males have longer front legs with dark fringes and swollen pedipalps; females are broader in the abdomen.

Eggs and egg sac

The female seals herself into a dense silk retreat — between drawn-together leaves, under a stone, in a curl of bark or in a crevice — and lays her eggs there in a papery sac. A single sac from a large female can hold around a hundred small, rounded eggs. She stays with them, guards them and feeds little until they hatch.

Spiderlings

The spiderlings remain inside the sac and the maternal retreat through their first moult, then disperse into the surrounding vegetation and start hunting at once. Juveniles are far duller than the adults, in brown and grey tones, and only develop the full red coat over the last moults — which means a small brown jumper in the same field may well be a young cardinal jumper. Growth runs through a series of moults, described in our guide to spider moulting.

Hunting and the use of silk

Cardinal jumpers build no capture web; no member of the family does. The hunting sequence is visual from start to finish: the wide-angle side eyes pick up movement, the spider rotates to bring the big forward eyes to bear, judges the distance, creeps into range and pounces. Silk is still produced constantly and used in three ways — a dragline anchored before each leap, which doubles as a safety line and a way of trimming the body angle in mid-air; a tent-like retreat for moulting, resting overnight and sheltering from rain; and the egg sac. Statements that jumping spiders “use silken threads to capture prey” confuse the dragline with a snare like an orb weaver's web.

Where the cardinal jumping spider lives

Phidippus cardinalis is an eastern and south-central North American species rather than a continental one. Records run from the mid-Atlantic and the lower Midwest south through the Appalachians and the coastal plain — Virginia, the Carolinas, Georgia, Florida, Tennessee, Alabama and Mississippi — and west into Texas and Oklahoma. It is nowhere especially abundant, and in most places it is a spider you find one at a time.

Its habitat is open and sunny: old fields, prairie remnants, pine flatwoods and open woodland, scrub, roadside verges, hedgerows and unkempt corners of gardens. It hunts on low vegetation, on tree trunks and on bare ground between plants, and it favours exactly the warm, dry, sparsely vegetated ground where velvet ants also run — which is the point of the mimicry. It is not a house spider and only enters buildings by accident.

Are cardinal jumping spiders venomous?

Yes, in the same trivial sense as almost every spider: the cardinal jumper injects venom to subdue insects. It carries no medical risk to people or pets. Salticid venom is tuned to small arthropod nervous systems and includes neither the tissue-damaging enzymes of the recluse spiders nor the vertebrate-active neurotoxins of the widow spiders. No jumping spider anywhere in the world is considered medically significant. The one genuine exception is an individual allergy to arthropod proteins, which reflects the person's immune system rather than the potency of the venom. The bright red coat advertises a sting the spider does not possess, so the colour is a bluff aimed at birds and lizards, not a warning to you.

Can a cardinal jumping spider bite?

It can, and at 10–13 mm it is large enough to break the skin, but bites are rare and always defensive — the spider has to be pressed, gripped or caught inside clothing. One that notices a hand will turn, watch, then run or drop away on its dragline long before biting.

A bite is a brief pinprick, leaving a small red spot with mild soreness that settles within hours. Wash with soap and water and apply a cold pack. Seek medical attention only if redness spreads, swelling is disproportionate, or there are allergic signs such as hives, dizziness or difficulty breathing.

Ecological importance and behavior of the cardinal jumping spider

The cardinal jumper is a day-active visual predator of open ground and low vegetation, taking flies, small moths, leafhoppers, plant bugs, beetles, crickets, cockroach nymphs and other spiders; a large female will attack prey close to her own size. Hunting on plant and soil surfaces rather than in a web removes insects a snare-builder never encounters.

A correction worth making: older fact tables list flies, crickets, fruit flies and roaches as this spider's predators. Those are its prey. Its actual predators are insectivorous birds, lizards, toads, mud-dauber and spider-hunting wasps that provision their nests with paralysed spiders, larger spiders, and parasitoid wasps that attack the egg sac.

Mimicry: the red-and-black pattern copies female velvet ants of the genus Dasymutilla — wingless mutillid wasps whose sting is famously painful and which most vertebrate predators learn to leave alone. The spider has no sting of its own, so this is Batesian mimicry: a harmless species profiting from the reputation of a dangerous one. The Apache jumping spider and several other southwestern Phidippus run the same bluff.

How the jump works: spiders lack extensor muscles in the key leg joints, so the spider raises its internal blood pressure and forces the hind legs straight. The leap is hydraulic, covers several body lengths, and is preceded by the anchoring of a dragline that acts as brake and tether.

Courtship and season: males display visually, waving the fringed front legs in front of the female. Adults are seen from late spring into autumn; the species overwinters as a well-grown juvenile and lives about a year.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• “Velvet ant” is the name of the wasp, not of the spider. Dasymutilla females are flightless mutillid wasps with a sting painful enough to earn the nickname “cow killer”; the cardinal jumper simply wears their livery. Older accounts that claim the spider itself is called a velvet ant have the mimicry the wrong way round.
• Mimicry only works where the model is common, which is why the reddest Phidippus species are concentrated in the warm, open country where velvet ants thrive.
• Jumping spiders swivel their retinas instead of their eyes: muscles inside the head move the tube-shaped retina of each large front eye, letting the spider scan a scene while sitting completely still.
• Salticidae is the largest of all spider families, with well over 6,000 described species — see the whole group on our jumping spiders page, from the zebra jumper to the regal jumping spider.

In summary, the cardinal jumping spider is a harmless, sharp-eyed hunter that has borrowed the warning colours of a stinging wasp. Nothing about its red coat is a threat to you — it is a message aimed at birds and lizards.