St Andrew’s Cross Spider

St Andrew’s Cross Spider

Family – Araneidae (Araneomorphae) ~ These spiders get their name from the shape of their web decorations, the white silk that they spin through the centre of the orb web in the shape of a cross. The spider also sits in the web with its legs in pairs forming the shape of a cross. Usually flying prey is caught in the web. Before biting their prey, all except the smallest prey is first wrapped up and secured in silk.

Interesting Facts –

The female has a silver, red, black and yellow back and two yellow stripes on her lower abdomen. Females’ bodies grow to about 16mm, and males’ to about 4mm.

The reason for the cross decoration in the web is not known. It is called the stabilimentum. It may be to do just that, to stabilise the web. However its blue white colour reflects ultra-violet light very efficiently which is thought to be important. This may be to attract insects that use ultra-violet light in their navigation.

One thing that is known is that when the spider is threatened it vibrates the stabilimentum until it and the spider becomes a blur, confusing predators.

Young spiders make a circular instead of cross-shaped stabilimentum which gradually becomes more cross-shaped as the young grow to adulthood.

Distribution –

Eastern Australia from rainforest margins to open environments in Queensland, New South Wales and Victoria.