Magnificent (Ordgarius magnificus)

Physical description and identification

The magnificent spider is the best known member of Ordgarius, a genus of orb weavers that long ago abandoned the wheel-shaped web. It was described from New South Wales material by William Joseph Rainbow in 1897 and is, for its size, one of the most striking spiders in eastern Australia — provided you find it. One point in older accounts needs correcting: the genus does not contain just two bolas species. As far as anyone has observed, every adult female Ordgarius hunts with a bolas.

Adults

• Size: adult females have a body length of about 12–15 mm, the largest in the genus. Males are dwarfs of roughly 2 mm — near 0.08 in, not the 0.07 in that a conversion slip has spread online — which makes them perhaps a thousandth of the female's mass.
• Colour: the female is creamy white to pale yellow, glossy, and flecked with yellow and pink spots; the front of the head region is often washed with white and dull red. In torchlight she looks wet and faintly translucent. Males are plain, small and brownish, with no useful markings.
• Eyes: eight small eyes in two rows, the lateral pairs raised on low mounds. None is enlarged, which rules out the big-eyed daytime hunters that share the same shrubs.
• Distinctive features: a pair of blunt, rounded tubercles sits on the front of the abdomen — hard knobs that give the species its lumpy profile. The body and legs carry long, fine hairs, many of them vibration-sensitive, and the front legs are short and thick rather than long and slender.

Eggs and egg sacs

The egg sacs are large, brown and spindle-shaped, hung on tough silk stalks among foliage, often several from the same twig so they look like a bunch of dried fruit. Each holds hundreds of eggs, and a female may build a series of them across a season. The frequently repeated figure of a 5 cm sac comes from a unit slip in the older literature; the sacs are large for the spider but closer to 2–3 cm long.

Spiderlings

Spiderlings emerge pale and smooth and darken with successive moults. They leave the natal twig by ballooning on silk. Like the tiny adult males, juveniles are far too small to manage a bolas and take minute flying insects instead, only switching to the adult hunting method once they are large enough to hold a swinging droplet.

How she hunts

Shortly after dark the female spins a short horizontal trapeze line between twigs and hangs beneath it by her back legs. She then produces a single vertical thread of silk tipped with a drop of exceptionally sticky, slow-drying glue: the bolas. From glands on her body she releases volatiles that imitate the sex pheromone of particular female moths. A male moth, following the scent plume upwind, flies within reach; the spider swings the bolas in a short arc, the glue grips his scaled wing or body, and she hauls the line in and bites. This is aggressive chemical mimicry, and it explains her diet exactly: almost nothing but male moths. She builds no capture web of any kind, which sets her apart from every ordinary member of the orb-weaving family.

Where the magnificent spider lives

Ordgarius magnificus is endemic to eastern Australia. Records run from southern and coastal Queensland through New South Wales and into Victoria, following the wetter forested country east of the divide rather than the dry interior.

The spider keeps to trees and tall shrubs, usually within about two metres of the ground: open eucalypt forest, rainforest margins, heath, regrowth scrub, and the shrub layer of orchards and suburban gardens. What she needs is a leaf or twig to rest under by day and an open pocket of air beneath it in which to swing at night. She is almost certainly more common than records suggest, because a motionless white lump under a leaf is invisible unless you are looking for it, and the hunting happens in the dark.

Are magnificent spiders venomous?

Yes, in the ordinary sense that nearly all spiders are venomous: the magnificent spider uses venom to subdue the moths it catches. It is not medically significant to people or pets. The venom is tuned to insects, no antivenom exists or is needed, and no serious envenomation has been recorded. This is not a relative of the Australian funnel-webs or of the redback, and it carries nothing comparable to those venoms.

Can magnificent spiders bite?

In principle yes, but in practice a bite is close to a non-event. The spider is small, slow-moving and reclusive, her fangs are short, and her response to being disturbed is to pull her legs in and drop on a dragline. Verified bites are essentially unrecorded. Anecdotal reports from bolas spiders describe a brief pinprick and a little local redness that fades within hours, without lasting effects. Wash the site with soap and water, use a cold pack if it is sore, and seek medical advice for any bite that swells dramatically or spreads, which would indicate an allergic reaction rather than the venom itself.

Ecological importance and behavior of the magnificent spider

The magnificent spider is a specialist predator of night-flying moths, and because the lure copies particular pheromone blends, an individual effectively targets a handful of species rather than whatever happens by. Several of the moths concerned are crop and garden pests, so a spider in a hedge or orchard edge provides unusually precise pest control. Older accounts that list butterflies among the prey are mistaken: butterflies fly by day and take no notice of a moth sex pheromone.

Natural predators: birds are the main threat, and the bird-dropping disguise is the answer to them. Spider-hunting and parasitic wasps take adults and attack egg sacs, and ants, lizards and larger spiders account for the rest. The tiny wandering males are the most vulnerable stage of all.

Prey–predator dynamics: the fine hairs on her legs are vibration detectors, and they tell her a moth is approaching before she can see it — the cue that times the swing. Because she exploits the moths' own communication channel, the system is an evolutionary arms race, with selection acting on moth pheromone blends and on the spider's ability to match them.

Seasonal behaviour: adults are found chiefly in the warmer months, with egg sacs appearing from late summer and spiderlings dispersing in spring. Most individuals live about a year.

Relationship with humans: entirely benign. She does not enter houses, never strings a web across a path, and cannot reasonably be bitten by accident. Finding one in the garden is a small piece of luck; the right response is to leave her alone and come back with a torch after dark.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• William Joseph Rainbow, who described the species in 1897, was the Australian Museum's arachnologist and named hundreds of Australian spiders.
• The hairs on her legs are vibration sensors sensitive enough to register an approaching moth in still air, which is what makes the swing of the bolas so well timed.
• The glue on a bolas droplet stays workable far longer than ordinary orb-web gum, letting her hold one ready for an hour or more.
• Because the lure is chemical rather than visual, she catches the same moth species that a pheromone trap in the same hedge would catch — the observation that first revealed what bolas spiders were doing.
• The disguise cuts both ways at no cost: it hides her from birds by day, and the moths she hunts at night are following a scent, not looking.

In summary, the magnificent spider is an orb weaver that gave up the orb and replaced it with chemistry. She counterfeits a moth's mating signal, swings one drop of glue at whatever answers, and spends the daylight hours disguised as a bird dropping — a remarkable animal that poses no risk whatever to people.