St Andrew’s Cross Spider Graham Winterflood/Flickr

St Andrew’s Cross Spider

Argiope keyserlingii

Did You Know?

  • Many males are attacked and eaten by the female during courtship!
  • Its predators include birds and humans (who destroy the webs), with wasps and flies known to target egg sacs
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This spider is named for the cross the female weaves into the web. There are many theories about why the female does this including, strengthening the web, for camouflage, and for increasing prey catches as the cross reflects ultra-violet light which attracts insects. It may also deter predators which must go to the effort of cleaning off the extra silk after diving into the web.

The female has a silvery head with silver, yellow, red and black bands across its abdomen, and two yellow stripes running down its underside. Its legs are dark brown to black with one or two yellowish bands. The male and juveniles are brown and cream, with brown legs. It often appears to have only four legs because it sits with its legs in pairs along the stabilimentum.

Distinctive feature

The zigzag patterns (known as the stabilimentum) it weaves into its web to form an X or a cross, after which it is named.

Size

Females 1 – 2 cm long but the tiny males are only 3 – 5 mm long (body length).

Behaviour

Diet

Insects, including flies, moths, butterflies, grasshoppers and bees caught in its web, which is strung between low shrubs and long grass. The prey is wrapped in silk and eaten straight away or hung nearby for later, although smaller prey may be bitten first.

Movement

The female usually hangs upside down on the underside of the web, in the centre, with its legs resting in pairs and placed along each arm of the webbed cross. It occupies the web continuously and is active at various intervals throughout the day and night. If threatened, it will either drop from the web or shake the web so vigorously that it and the webbed cross become a blur, confusing any potential attacker. The male usually builds a smaller web close to the female, or sits on the outskirts of the female’s web, on the top side.

Breeding

From summer to autumn. Several males will often sit on the upper outskirts of a web, on the opposite side to the female, waiting for an opportunity to mate with her. The male constructs a mating thread within the web which he vibrates to attract the female. After mating, the female wraps several pear-shaped, green egg sacs in a network of silk and suspends them in nearby vegetation or from a wall.

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What to Observe

  • How many Females

  • Number of Males on the web

  • Egg sacs in web

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When and Where

When To Look

Day or night throughout summer when they are most prevalent and also in autumn.

Where To Look

  • In eastern Australia, including Queensland, NSW and Victoria
  • In a variety of habitats including rainforest edges, open forest, woodlands, grasslands and urban areas; particularly common in suburban gardens
  • Look between low shrubs and long grass, and also against the walls of buildings
  • Its web is commonly 1 – 2 metres above the ground (generally around waist height) and about one metre in diameter
  • Look in your backyard garden during summer
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What Else?

Similar Species

Painted Orb Weaver (Argiope picta) less common than the St Andrew’s Cross Spider and doesn’t normally produce a complete X pattern on its web.

Banded orb-weaving spider (Argiope trifasciata) has yellow, white and black bands on its abdomen, and dark brown and pale yellow bands along the entire length of its legs.