Hyllus Diardi

Physical description and identification

Hyllus diardi is a heavyweight among the jumping spiders. It does not have the longest legs in the family, but it is bulky, densely furred and unusually solid for a salticid, which is exactly why it picked up the common names heavy jumper and giant jumping spider. The genus Hyllus contains some of the largest jumping spiders in the Old World, and this is the species most often photographed in Southeast Asia.

Adults

• Size: adult females usually measure about 10–15 mm (0.4–0.6 in) in body length, with males a little smaller and noticeably slimmer. That is several times the bulk of a common garden jumper.
• Colour: the sexes differ. Females are clothed in dense pale grey to greyish-white scales, with faint darker bands or chevrons on the abdomen and a lighter median stripe. Males are darker — brown to nearly black — with sharper white markings, a pale band across the front of the carapace and a conspicuous fringe of white hairs below the eyes. The frequent description of the species as simply “grey-white” fits the female and understates how different a mature male looks.
• Eyes: eight eyes in the salticid pattern of four rows. Two huge anterior median eyes face directly forward and give this spider its famously good sight; a smaller pair flanks them, a tiny pair sits behind, and a fourth pair near the rear of the carapace watches for movement from behind. Together they cover almost the full circle. Our guide to spider eyes sets out the arrangement.
• Distinctive features: a high, squared-off carapace, stout forelegs used to grip struggling prey, and robust chelicerae that are iridescent green or bronze in fresh adults. Males have swollen pedipalp tips; females have a broader abdomen.

Eggs and egg sac

The female spins a closed silk chamber under a curled leaf, in a bark crevice or in a sheltered corner, lays her eggs inside it and guards them until the young disperse. The retreat is thick, opaque and tightly sealed, so the eggs themselves are almost never visible from the outside.

Spiderlings

Hatchlings are pale and soft, with the adult eye arrangement already in place, and darken as they feed and grow. They remain inside the maternal retreat through their first moult before leaving to hunt alone. Popular accounts describing spiderlings jumping about inside the egg sac are not accurate: newly hatched salticids are immobile and defenceless until their first moult hardens them. Growth continues through a series of moults, each carried out inside a fresh silk chamber — see spider moulting.

Hunting, not a web

This spider builds no snare of any kind. It hunts the way the rest of its family does: it walks over leaves and bark, stops, swivels to bring a moving target into the field of the big front eyes, closes the distance in short creeping steps and then leaps onto the prey, seizing it with the forelegs and biting immediately. The leap is hydraulic — spiders lack extensor muscles in the main leg joints and straighten their legs by a surge of internal fluid pressure — and a silk dragline is fixed to the surface before every jump so that a miss ends on a rope rather than on the ground. Silk is otherwise used only for retreats and egg sacs; see spider webs for how this differs from a snare-building spider.

Where Hyllus diardi lives

The species is widespread across tropical South and Southeast Asia. It is recorded from India and Sri Lanka eastward through Myanmar, Thailand, Laos, Cambodia and Vietnam to southern China, and south through peninsular Malaysia, Singapore and Indonesia. It is one of the most frequently photographed spiders in the region, largely because it is big, active by day and unbothered by an approaching camera.

Habitat is broader than the “mangrove vegetation and wasteland” often quoted for the species. Hyllus diardi turns up on shrubs and low foliage, on tree trunks and fence posts, in secondary growth and scrub, at mangrove margins, and routinely in plantations, parks and gardens. What it needs is a sunlit vertical or near-vertical surface with plenty of insect traffic, since it hunts by sight and needs light to do it. It is a daytime animal and will bask, which is why sightings peak on warm, bright mornings.

Are Hyllus diardi spiders venomous?

Yes, in the same sense that nearly every spider is venomous: Hyllus diardi injects venom to kill the insects it catches. It has no medical significance for people. Jumping spiders have small, insect-adapted venom and are not related to the widow spiders or the recluses, and none of the roughly 6,000 described salticids is regarded as dangerous to humans. No antivenom exists for the family and none is required.

Can Hyllus diardi spiders bite?

They can, and because this is a large spider the bite is more noticeable than that of a small jumper — but it still is not dangerous. Bites happen only when the spider is trapped against skin, for instance when it is grabbed or caught in clothing. The realistic outcome is sharp local pain, a small raised welt and redness at the site, settling within a day. Wash the area with soap and water, apply a cold pack and keep it clean. Seek medical advice only if the swelling spreads well beyond the bite, or if signs of infection appear over the following days.

A jumping spider is far more likely to look at you than to bite you. The standard reaction to a hand is to turn, watch, and then side-step around a leaf or drop on its dragline.

Ecological importance and behavior of Hyllus diardi

This species is a generalist diurnal predator of foliage and bark. It takes flies, small moths, bugs, beetles, grasshopper nymphs, ants and other spiders, and its size lets it handle prey that smaller jumpers cannot. On plantation and garden vegetation that makes it a useful natural check on plant-feeding insects.

Natural predators: insectivorous birds and lizards are the main threats by day, and spider-hunting wasps of the family Pompilidae and mud daubers paralyse adults to stock their nest cells. Mantises, ants and larger spiders take individuals opportunistically.

Prey–predator dynamics: because it hunts by sight in the open rather than waiting in a snare, it occupies a different layer from the web builders around it, cropping active, fast-moving insects that rarely blunder into a web. Its own escape strategy is the same one it hunts with — a jump, backed by the dragline.

Courtship: mature males court by sight. A male that spots a female raises and waves his front legs, vibrates his abdomen and advances in a stiff, jerky, side-to-side dance, all of it aimed at the female's enormous front eyes. Getting it wrong is dangerous: an unreceptive female may attack. Successful courtship is followed by the female sealing herself into a retreat with the egg sac.

Relationship with humans: entirely benign. The species is harmless, easy to approach and among the most popular subjects for macro photographers in Asia. It occasionally wanders onto a wall or window frame, but it does not colonise houses and needs no control.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• Jumping spiders see better than any other animal of comparable size. The huge front eyes are long tubes with a layered, four-tier retina that the spider sweeps from side to side with internal muscles — a moving scan rather than a fixed image.
• The leap is powered by fluid pressure, not muscle. Spiders have no extensor muscles in the crucial leg joints and straighten their legs hydraulically, which is why a spider can jump many times its own body length from a standing start.
• Every jump starts with a safety line. The spider fixes a dragline before it launches, and can use the tension in that line to steer its body in mid-air.
• The species was described in 1837 by the French naturalist Charles Athanase Walckenaer, and the name commemorates the traveller and naturalist Pierre-Médard Diard.
• Its reputation as a giant is about weight, not span. Hyllus diardi is one of the bulkiest salticids in Asia, but plenty of other spiders cover far more ground with their legs.

In summary, Hyllus diardi is a large, sharp-eyed, day-hunting jumping spider of tropical Asia that catches its prey by stalking and leaping rather than by spinning a web. It is harmless to people, useful in gardens and plantations, and one of the most approachable spiders in the region.