St Andrews Cross Spiders
A Very Special Spider
Before you get worried about spiders in the garden, it might just pay to take a closer look (from a safe distance of course). If it's a St Andrew's Cross Spider hanging around, you're in luck!
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 bit of mystery. It was first thought to add strength to the web and make it more stable, but more recent research seems to think that 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. Very cluey spiders!
When threatened, the St Andrew's Cross Spider drops from the web (bungee jumping with a safety line) 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, which is also a treat to sneak a peek at. Click here to see a picture of it.
Female St Andrew's Cross Spiders are also very photogenic because of their fantastic colours. 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. If you count the legs, males grow up to 15 mm from leg to leg - about the size of the female's body, not including her long, long legs!
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, so watch where you walk when you step out into the garden this summer so that you can enjoy your buddies rather than getting a fright from them.
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.
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. You won't have the prettiest backyard buddies showing up in your garden unless you have their animal and plant food sources around too - so it pays to have lots of different buddies in the garden.