Backyard Buddies
St Andrews Cross Spiders

Photo: James Niland

St Andrews Cross Spiders

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St Andrew's Cross Spiders are fantastic backyard buddies as they spin big webs that easily snare insects such as flies, mosquitoes, moths and other bugs. They are not aggressive towards people and their bite is not toxic.

The webs of St Andrew's Cross Spiders are also fascinating to look at because of their decorations. These spiders get their name from the bluish-white cross pattern that they create in the centre of their web, which looks like the St Andrew's cross on the Scottish flag.

The purpose of the cross decoration has long been a mystery. It was first thought to add strength to the web and make it more stable, but more recent research suggests it assists with attracting prey. This cross reflects UV light very strongly and draws in flying insects, which use UV light to locate food sources like flowers and navigate amongst vegetation.

The cross on the web also confuses predators into thinking the spider is much larger than it is, and warns them to stay away as the effort required from a bird to remove the sticky web from its feathers after attempting to catch the spider is considerable.

When threatened, the St Andrew's Cross Spider drops from the web or shakes it so vigorously that both the spider and its cross become a blur, confusing the attacker.

Young spiders don't make the distinctive cross on their webs, but instead create a wild and crazy zigzag pattern around the centre of the web .The female grows up to 16 mm in body length and has a silver, yellow, red and black banded upper abdomen with two longways yellow stripes below.

Males are a bit less exciting, as they are mainly brown and cream coloured. Like most male spiders they are smaller than the female, and only grow up to 4 mm in body length.

Adult females build webs up to 1 m across usually in front of a bushy plant. Click to watch a video of a St Andrew's Cross Spider building her web. Their webs are usually about 1-2 m above the ground.

Did you know? 

Male St Andrew's Cross Spiders put their life on the line to mate with a female. They can sometimes lose legs in the encounter. If they're lucky enough to escape afterwards, they can regrow lost legs over time.

Tip

It's great to have insects and spiders around your garden. Spiders will control your insect numbers, but both spiders and insects will also be a great food source for lizards and birds such as Silvereyes and Friarbirds. 

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Quote

”Birds, bugs, lizards and penguins are my favourite Backyard Buddies – I like to find, watch and learn about what they do and what I can do to help them.“

Gus – 11 year old Backyard Buddy, NSW

Photo: OEH