St Andrew's Cross spider fact sheet | Field of Mars EEC

What are St Andrew's Cross spiders?

St Andrew’s Cross spiders are native Australian orb-weaving spiders. Their scientific name is Argiope keyserlingi.

They are named after the bright white silk cross that is often found in the centre of their web. This cross is called a stabilimentum. The spider often sits in the middle of the web with its legs held together in pairs, making its body look like part of the cross.

Females are much larger and more colourful than males. Females have banded legs and a silver, yellow, red, black and white abdomen. Males are much smaller and are usually brown or cream.

St Andrew's Cross spiders are often found on their webs in an X shape.

Where do St Andrew's Cross spiders live?

St Andrew’s Cross spiders are found in eastern Australia, including Queensland, New South Wales and Victoria. They live in habitats with low shrubs, grasses and other plants that can support their webs.

They may be found in gardens, open forest, heathland, shrubby bushland and rainforest edges. Females build medium-sized orb webs on low vegetation and usually stay in the web during the day and night.

At Field of Mars Reserve, shrubby bushland and garden edges provide habitat for many web-building spiders. These areas support insects for spiders to eat and plants that can hold their webs.

Females are often found in low vegetation where they can build orb webs between stems and leaves.

What do St Andrew's Cross spiders eat?

St Andrew’s Cross spiders eat insects that become trapped in their sticky orb webs. Their prey can include flies, moths, butterflies, bugs and bees.

When an insect lands in the web, the spider senses the movement through the silk. It moves towards the prey, wraps it in silk and then bites it. Smaller prey may be bitten before being wrapped.

Spiders are important predators in bushland and gardens because they help control insect populations.

St Andrew’s Cross spiders use sticky silk webs to trap flying insects.

What is the life cycle of a St Andrew’s Cross spider?

St Andrew’s Cross spiders hatch from eggs as tiny spiderlings. They grow by moulting, which means they shed their outer skeleton as their bodies become larger.

Mating usually occurs from summer to autumn. A male approaches the female carefully and may vibrate a silk thread to attract her attention. This can be dangerous because the female may attack or eat the smaller male.

After mating, the female makes a greenish, pear-shaped egg sac. She hangs it in silk, often among leaves near the web. Many small spiderlings hatch from the egg sac.

The spiderlings stay close together for a short time before dispersing. Some climb to a high point and release silk into the air. The breeze can carry the silk and spiderling to a new location. This is called ballooning.

Young St Andrew’s Cross spiders may build a circular white silk pattern in the centre of their web. As they grow, this pattern changes into the more familiar cross shape.

Male St Andrew’s Cross spiders are much smaller than females.

Females make greenish egg sacs that are hung in silk near the web.

Many tiny spiderlings can hatch from one egg sac.

Young St Andrew’s Cross spiders may build circular silk decorations before making the adult X-shaped cross.

What adaptations do St Andrew’s Cross spiders have to help them survive?

St Andrew’s Cross spiders have several adaptations that help them survive. Their large orb web is a sticky trap for catching flying insects. Fine sensory hairs on their legs help them detect vibrations when prey lands in the web.

The bright white stabilimentum may help attract insects or make the web easier for birds and other animals to see. It may also make the spider look larger or harder for predators to target.

If threatened, a St Andrew’s Cross spider may drop from the web on a silk line. It may also shake the web rapidly so the spider and silk cross become a blur. This can confuse predators and give the spider time to escape.

The bright silk cross may help attract prey or protect the spider from predators.

Why are St Andrew’s Cross spiders important?

St Andrew’s Cross spiders are important predators. They catch insects in their webs and help keep insect populations balanced in bushland, parks and gardens.

They are also part of the food web. Birds, wasps and other predators may eat spiders, while some wasps use spiders as food for their larvae.

St Andrew’s Cross spiders also show why shrubs and layered vegetation are important habitat. Low plants provide web-building places, shelter and feeding areas for many small animals. In healthy bushland, even small spaces between leaves and stems can become important habitat.

Mud dauber wasps can collect spiders as food for their developing larvae.

How can you help St Andrew’s Cross spiders?

You can help St Andrew’s Cross spiders by protecting habitat. Keep a variety of native plants, shrubs and grasses in gardens and bushland so spiders have places to build webs.

Avoid breaking spider webs when you see them. If a web is across a path, walk around it if it is safe to do so. Spiders use energy and silk to build their webs, and the web helps them catch food.

Avoid unnecessary pesticide use, especially around flowering plants and garden edges. Pesticides can reduce the insects that spiders eat and may also harm spiders directly.

If you find a St Andrew’s Cross spider, observe it from a safe distance. Watch how it sits in the web, responds to movement and uses silk to survive.

Protected areas provide safe places for spiders and native animals.

Related fact sheets

More invertebrate fact sheets

• Invertebrate fact sheets – overview
• Arachnids fact sheet – overview
• Golden orb weaving spider fact sheet – another orb-weaving spider with a large circular web.
• Leaf-curling spider fact sheet – orb-web spider that hides in a curled leaf in the centre of its web.
• Trapdoor spider fact sheet – contrast with a burrow-dwelling ambush spider.

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