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A cross to bear

February 8, 2023

One of the most striking of the orb-weaver spiders is the St Andrew’s Cross Spider (Argiope keyserlingi) pictured left. It is distributed along the east coast of Australia. Although I have seen many photos of them I had never seen one until last week when I came across a hakea festooned with them.

Although when at rest the spider holds its legs in the shape of a St Andrew’s Cross it is named for the zig zag ribbons of silk it weaves into its web in the shape of that cross. In the picture below right the beginnings of the cross can be seen in the bottom left.

The reasons for the web decoration are not understood. One theory is that the silken cross is where the spider places its legs when on the web. Another theory proposes that the silken ribbon reflects extra UV light which is an attractant for insects. The cross could also be a device to make the web more obvious so that larger creatures such as birds don’t fly into it.

What we do know is that if we found a St George’s Cross Spider the web design will be a monochrome Union Jack.

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