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St Andrew's Cross Spider - Argiope KeyserlingiFAMILY ARANEIDAEThis page contains pictures and information about St Andrew's Cross Spiders that we found in the Brisbane area, Queensland, Australia.
St Andrew's Cross spider is easily found in Brisbane bushes and backyard gardens. It is easily recognized by the pattern on its body and its web. The spider makes an orb web, in the middle it makes four thickened zigzag strips in the shape of a cross of 'X'. The spider then hangs head down with its legs pairs together over the cross. This is why it called St Andrew's cross spider. Adult females build vertical orb web about 1m in diameters. The spiders active both day and night. St Andrew's Cross spider and some other spiders make this zigzag band known as stabilimentum. The function is uncertain yet. Some believed that the zigzag is used as the sign to warn-off the larger animals. Some believed that it is to stabilize the web. Some suggested that it act as a sunshade. This is a typical type of question in Evolution, it may never have a proven answer. However, more than a single, or even all answers are correct. Sometimes, the St Andrew's Cross spider makes only one line. Sometimes, not very often, the spider make two crosses.
Adult male St Andrew's Cross spiders are smaller than the adult female. They have the relatively smaller abdomen, with no pattern on their abdomen. Both female and male St Andrew's Cross spiders have their hairy silver thorax and banded legs. All St Andrew's Cross spiders, including male, young and matured female, rest with legs in pairs. We sometimes found male St Andrew's Cross spider with some of its legs loss. Like this male only four legs left. We believe he was just mate with a female. Although he was lucky enough to escape after mating, half of its limbs were broken.
St Andrew's Cross spiders build vertical orb webs. The adult female build the web about half a meter to one meter in diameter, usually 1-2 meters about ground. Some orb web spiders, such as the Garden Orb Web Spiders, only set up their web at night, but the St Andrew's Cross spiders set up their web and 24 hrs standby. However, they usually rebuild their web at mid-night if necessary. In day time St Andrew's Cross spiders usually only repair (at minimum level) their webs if damaged. |
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