Lobed Argiope (Argiope lobata)

Physical description and identification

The lobed argiope is the easiest member of the genus Argiope to name on sight. Instead of the neat oval or wasp-striped abdomen of its relatives, an adult female carries a broad, flattened, chalky-white abdomen whose margins are cut into deep rounded lobes, like the edge of an oak leaf. Nothing else in the Mediterranean or African orb weaver fauna looks like it.

Adults

• Size: females measure about 15–25 mm in body length, occasionally a little more, which makes this one of the largest orb weavers in southern Europe. Males are dwarfs at 4–6 mm and are easy to overlook at the edge of the female's web.
• Colour: the upper surface of the abdomen is silvery to creamy white with fine dark spots and a scatter of pale yellow or buff patches. The underside is very different: dark brown to black with two bright yellow bands and paired light spots. Legs are ringed dark brown and pale yellow, and the carapace is covered in dense silver-white hairs. Descriptions of "red and black spots" come from confusion with other Argiope; red is not a normal feature of this species.
• Eyes: eight small eyes in two rows, the lateral pairs set close together on slight bumps. None is enlarged.
• Distinctive features: six to seven pairs of blunt lobes along the sides and rear of the abdomen, matched by shallow ridges across the top. The silhouette is flat and broad rather than round, and the whole animal looks as though it has been pressed from chalk.

Eggs and egg sac

The female builds her egg sac herself, on her own web lines or in the vegetation beside them — males do not build webs for females, and that part of the older literature is simply wrong. The sac is an urn- or pear-shaped capsule of tough brown-grey silk, 20–30 mm across, with a papery outer wall that sheds rain. A large female packs several hundred eggs into one, and the biggest sacs recorded hold roughly a thousand.

Spiderlings

The eggs develop in autumn and the young remain inside the sac through the winter, insulated by a loose mass of fluffy silk. They come out in spring, hang together briefly in a tangle near the sac, then climb to a high point, spin out silk and drift away on the wind — see spider ballooning for how that works. The mother is long dead by then.

The web

The web is a large vertical orb, often 40–60 cm across and slung a metre or two above ground between shrubs, cactus pads, fence wires or tall dry grasses. Here is the surprise: unlike the wasp spider and most of its other relatives, an adult female Argiope lobata normally builds no zig-zag stabilimentum at all. Juveniles typically add a dense disc of white silk at the hub and lose the habit as they grow. Where one is present on an adult web it is a short ragged remnant, not the bold ribbon people expect. The orb is rebuilt frequently, often before dawn. See our guide to spider webs for the building sequence.

Where the lobed argiope lives

Argiope lobata has one of the widest ranges of any orb weaver. It occurs right around the Mediterranean — Portugal, Spain, southern France, Italy, Greece, Malta, Cyprus and Turkey — and through the Middle East, including Israel. Southward it runs across North Africa and down through the Sahel and East Africa to South Africa and Namibia, and eastward across the Arabian Peninsula, Iran and Central Asia to India. It also reaches the Canary Islands and Madagascar.

The habitat is consistently dry and sunny: garrigue and maquis scrub, sand steppe and steppe grassland, semi-desert with scattered bushes, olive and citrus groves, vineyard margins, coastal dunes and the weedy edges of gardens. The spider needs stiff vegetation two anchor points apart and plenty of low-flying insects, which is why the richest populations are along field edges and dry watercourses rather than inside closed woodland.

Is the lobed argiope venomous?

Yes, but not in a way that matters to people. Like all Argiope, it uses venom to subdue insects, and the venom is dominated by acylpolyamine toxins that block glutamate receptors in the insect nervous system. One of those molecules, argiotoxin-636, was isolated from Argiope lobata and is now a standard laboratory tool in neuroscience for studying the same receptor family in vertebrates. That research value has nothing to do with human risk: the quantities involved are minute, there are no recorded systemic envenomations, and no antivenom exists or is needed.

Can lobed argiope spiders bite?

They can, but bites are genuinely rare. A disturbed female shakes her web hard enough to blur her own outline, then drops to the ground on a dragline and stays still. Biting requires the spider to be grabbed or trapped — typically by someone picking it off the web by hand, or by a hiker who catches one inside a shirt collar.

The result is a sharp pinprick with local redness and swelling, sometimes a little itching, which settles within hours. Wash the area, apply a cold pack and leave it alone. Seek medical advice only if the site shows signs of infection over the following days, or if there are signs of an allergic reaction such as spreading hives or breathing difficulty, which are individual responses rather than effects of the venom.

Ecological importance and behavior of the lobed argiope

The lobed argiope is an ambush predator tied to its web. The female hangs head-down at the hub with her legs on the radii, feeling the tension in each thread. When an insect strikes, she runs out, swathes it in broad bands of silk drawn out with the hind legs, and only then bites. Wrapping before biting is the standard Argiope sequence and it lets her take grasshoppers, wasps and bees that would injure a spider attacking head-on.

Diet: grasshoppers and locusts, crickets, bees and wasps, flies, beetles, moths and butterflies. In dry farmland this makes the species a useful, free-of-charge control on orthopteran pests. Prey that is too large or too heavily armoured is cut out of the web and dropped.

Natural predators: birds are the main threat to adults; spider-hunting wasps of the family Pompilidae paralyse orb weavers to provision their burrows; mantises, lizards and parasitoid wasps take their share. Egg sacs are attacked by parasitic wasps and flies whose larvae eat the developing eggs from inside.

Mating and seasonal behaviour: females mature in mid to late summer. The tiny males live at the periphery of a female's web and approach carefully, plucking the silk in a courtship rhythm, often timing the attempt to the moments after her final moult. Sexual cannibalism is frequent in the genus, and a male's palp is commonly broken off inside the female, plugging her and reducing his rivals' chances. Adults die with the first cold weather; the species overwinters as eggs and spiderlings inside the sac.

Relationship with humans: harmless and useful. Most encounters happen when someone walks into the web on a path, and the spider is the more disturbed of the two.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The species was described in 1772 by Peter Simon Pallas, the Berlin-born naturalist who spent most of his career exploring the Russian Empire. He placed it in the catch-all genus Aranea; it moved to Argiope when Audouin erected that genus in 1826.
• Argiope is a name from Greek myth meaning roughly "silver-faced", and the dense white hairs on the carapace of this species make the point better than any other member of the genus.
• Argiotoxin-636, first isolated from the venom of this spider, helped establish how polyamine toxins block glutamate receptors — work that fed directly into modern research on excitatory signalling in the brain.
• The abdominal lobes are not armour. They are extensions of a soft body wall, and a well-fed female shortly before egg-laying is so swollen that the lobes flatten out and become hard to see.
• Because adults usually build no stabilimentum, this species is the standard comparison in studies asking what silk decorations are actually for: a close relative that manages perfectly well without one.

In summary, the lobed argiope is a large, dramatic and entirely harmless orb weaver of hot, dry, open country across three continents. The scalloped chalk-white abdomen identifies it instantly, and an adult sitting in an undecorated orb is behaving exactly as it should.