Peacock (Maratus)

Physical description and identification

Maratus is a genus of very small jumping spiders in which the males have evolved some of the most elaborate visual ornament found in any animal. More than a hundred species are described, and the total keeps climbing: the great majority have been named since 2010, largely from photographs and specimens collected by field naturalists in southern Australia. Identification to species is almost always done from the male's fan pattern, because the females of many species cannot yet be told apart.

Adults

• Size: among the tiniest spiders anyone goes looking for. Body length runs from about 2.5 mm to around 6 mm, most species sitting at 4–5 mm. A peacock spider fits on a fingernail with room to spare, which is why so few people ever see one in the wild.
• Colour: males carry a plate of dense coloured scales across the top of the abdomen — blues, violets, reds, oranges, creams and blacks in species-specific patterns. Females and juveniles of both sexes are cryptic brown, grey and cream with mottled scales. Not every male is bright to human eyes: M. vespertilio, for example, is a subdued brown with iridescence confined to the side flaps.
• Eyes: the standard salticid arrangement, with a huge forward-facing pair dominating a broad, flat face. The genus has the acute colour vision the family is known for, and the display is built to be read by it; see our guide to spider eyes.
• Distinctive features: in most species the male's abdominal plate has hinged lateral flaps that fold away at rest and unfold into a disc during display, and the third pair of legs is elongated, banded and tipped with brushes. The abdomen joins the cephalothorax by a long, flexible pedicel, which is what lets the male tilt the fan vertically over his own back.

Eggs

After mating the female builds a small silk retreat — under bark, a stone, or deep in leaf litter — and lays a modest clutch of a few eggs inside a silk sac. She stays with the sac and guards it until the spiderlings emerge, and may produce more than one clutch in a season.

Spiderlings

Hatchlings are brown and patterned like females and stay in the maternal retreat for around two weeks before dispersing. Males acquire their colours gradually through successive moults, and the full fan appears only at the final moult to adulthood, so a brown Maratus is not necessarily a female.

No webs, but plenty of silk

Like other jumping spiders, Maratus builds no capture web. It hunts entirely by sight, walking through litter and low vegetation, fixing on prey with the principal eyes, stalking and pouncing. Silk is still used constantly: a dragline is laid as the spider moves and anchored before every jump, and silk retreats serve for shelter, moulting, egg-laying and overwintering.

Where peacock spiders live

Maratus is an Australian genus. Species occur in every state, but diversity is concentrated in the southern half of the continent, with hotspots in southwestern Western Australia and in the southeast across Victoria, New South Wales and South Australia. One species, M. griseus, is also recorded from New Zealand. A Chinese species long listed in the genus as M. furvus has since been shown not to belong to Maratus at all, so the older claim that the genus reaches China is out of date. For the wider picture see our guide to spiders in Australia.

The habitats are dry and open rather than forested: heath, mallee and dry sclerophyll woodland, coastal dunes, grassland, granite outcrops and the litter beneath shrubs. Several species are confined to very small areas, which makes habitat clearance a real conservation concern for a genus most people know only from video clips.

Are peacock spiders venomous?

Yes, in the way that virtually every spider is venomous: Maratus injects venom to subdue the flies, moths, crickets and small spiders it catches. That venom has no medical significance whatsoever for humans or pets. It is not related to the widow, recluse or funnel-web venoms, no antivenom exists or is needed, and no envenoming by a peacock spider has ever been documented. The practical limit is mechanical as much as chemical: the fangs of a 4 mm spider are barely able to engage human skin.

Can peacock spiders bite?

For practical purposes, no. A peacock spider's response to anything as large as a person is to run, to sidestep around a stem, or to jump clear. Even if one were held firmly, its fangs are so short that a bite would usually register as nothing at all, and at worst as a momentary pinprick with no swelling. There is no first aid to describe beyond washing the spot.

Ecological importance and behavior of peacock spiders

Peacock spiders are daytime sight-hunters of the ground layer, taking flies, small moths, crickets, leafhoppers and other spiders, sometimes prey larger than themselves. They are a small but real part of the invertebrate predator community in Australian heath and woodland, and in turn they feed birds, lizards, mantises, ants, assassin bugs, wasps and larger spiders.

The courtship display: this is what the genus is famous for, and it is multimodal. A male that sights a female raises his abdomen vertically, unfolds the lateral flaps into a full disc and waves his elongated third legs in a species-specific rhythm, shuffling sideways to keep the fan square-on to her eyes. At the same time he drums and buzzes against the substrate, producing vibration signals that travel through litter and sand and that researchers record with laser vibrometry. Pattern, motion and vibration are assessed together; a male who gets the sequence wrong is ignored, chased off, or occasionally eaten.

How the colours are made: two systems are at work. Reds, oranges and creams come from pigments in the scales. Blues and violets come from structure — layered nanoscale architecture in modified scales that bends light, as a butterfly wing or a soap film does. Some species add regions of "super black" cuticle covered in microscopic bumps that absorb almost all the light landing on them, so the colours beside them look more saturated than they physically are.

Natural predators and defence: bright colour is risky, and the display is directional for that reason — little of the fan is visible from behind or above. At rest the flaps fold away and the male is a drab brown speck.

Seasonal behaviour: the life cycle is annual. Adults appear in spring, roughly August to December depending on latitude, which is when displays can be seen; juveniles carry the population through the rest of the year.

Relationship with humans: harmless and, unusually for spiders, genuinely popular — they head most lists of the cutest spiders. Public enthusiasm has driven the discovery of dozens of species, and that now matters for conservation, because it is the main reason anyone is mapping where these spiders still occur.

Species in the genus and similar spiders

Quick facts

Did you know?

• The genus was named in 1878 by Ferdinand Karsch, a curator at Berlin's Museum für Naturkunde, who in the same year also erected Portia, the spider-eating jumping spiders.
• Maratus volans means "flying Maratus". Nineteenth-century naturalists assumed the unfolding abdominal flaps were wings of a sort, used to glide between plants. They are not; they are billboards.
• Some species carry patches of super-black cuticle textured with microscopic bumps that trap light, reflecting well under one per cent of what hits them. The effect makes the adjacent reds and blues look almost luminous.
• Claims that peacock spiders leap forty times their body length are not supported by measurement. Salticids of this size jump a few body lengths — the impressive part is the aim, not the distance.
• Many Maratus species were first spotted by amateur photographers and described scientifically afterwards, making this one of the few animal groups where public interest has directly driven discovery.

In summary, peacock spiders are four-millimetre Australian jumping spiders with an extraordinary visual and vibratory courtship, no capacity to harm anyone, and a number of species clinging to very small patches of habitat. They are worth protecting for more than their photographs.