The St. Andrew’s cross spider (Argiope keyserlingi) is named for its bright web decorations in the shape of a saltire. It spins a zig zag line of bluish silk in a cross shape through the centre of their web. It then sits in the centre of the web with their legs aligned along the arms of the cross.
The role of the cross-shaped pattern, which is called a stabilimentum, has long been a puzzle to spider experts. It was first thought that it strengthened the web, however it is now thought that it helps to attract prey. The threads of the cross reflect ultraviolet light in a similar fashion to some plants. It’s thought that flying insects mistake this ultraviolet light for a flower and are attracted onto the web.
Did you know?
Scotland has a long association with spiders. Robert the Bruce, feeling downtrodden and defeated in his battles with the English was apparently inspired to press on by the tenacity of a spider. The spider failed several times to link its web from one area to another but each time it failed it simply tried again until it succeeded! The spider’s persistence helped motivate Robert the Bruce to fight on to secure Scotland’s independence!
The St. Andrew’s cross spider is found in Australia; however one of its relatives, the Wasp spider (Argiope bruennichi) is an uncommon species that can be found in the south of England. The Wasp spider likes unmown grassland in general, especially where there’s a good population of grasshopper (Orthoptera). The overwintering eggsacs of this species are susceptible to damage by mowing, which is why it’s most commonly found on brownfield sites. These sites provide a home to many endangered or uncommon species. Buglife is currently working to conserve the Wasp spider, and other species that live on brownfield sites.
To find out lots more about spiders, click here
|Wasp spider (Argiope bruennichi) © Greg |
To access the Australian Museum's fantastic spiders page (including a factsheet on the St. Andrew's cross spider), please click here.