Argiope (spider)
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 St. Andrew's cross spider
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A. aetherea |
The genus Argiope includes rather large and spectacular spiders that have often a strikingly coloured abdomen. These are well distributed throughout the world, and most countries in temperate or warmer climates have one or more species, which look similar.
A. bruennichi, the "wasp spider
Dorsal and ventral images"
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[edit] Names
In North America, Argiope aurantia is known as the black and yellow garden spider. In England, Argiope bruennichi, where it is found only on the southern coast, and in other parts of Europe, including Germany, is also known as the wasp spider. The East Asian species Argiope amoena is known in Japan as kogane-gumo. In Australia, Argiope keyserlingi and A. aetherea are known as St Andrews Cross spiders, for its habit of resting in its web with its legs outstretched in the shape of an X, the traditional shape of the cross of St. Andrew. The large white zigzag in the centre of its web is called the stabilimentum or web decoration and its function is controversial.
In the eastern United States, Argiope species, especially A. aurantia, are more commonly known as writing spiders, due to the unique patterns that they build in their webs. In years past, it was sometimes called the "McKinley spider" because in the period before the election that brought McKinley to office someone claimed that the stabilimentum of one spider's web spelled out "McKinley."
[edit] Web
The average orb web is practically invisible, and it is easy to blunder into one and end up covered with a sticky web. The very easily visible pattern of banded silk made by Argiope is pure white, and the highly visible spider sitting in the center may be bright yellow on a field of black or variegated red white and yellow stripes.
These spiders build webs with centers that are just under 1 meter above the ground, so they are too low for anything larger than a rabbit to walk under. The overtness of the spider and its web may prevent larger creatures from destroying the web and possibly crushing the spider underfoot.
[edit] Reproduction
The male spider is much smaller than the female, and unassumingly marked. When it is time to mate, he spins a companion web alongside the female's. After mating, the female lays her eggs, placing her egg sac into the web. The sac contains between 400 and 1,400 eggs. These eggs hatch in autumn, but the spiderlings overwinter in the sac and emerge during the spring. The egg sac is composed of multiple layers of silk and designed to protect its contents from damage; however, many species of insects have been observed to parasitise the egg sacs.
[edit] Harmless
These spiders are spectacular and may be quite alarming if one is not familiar with them, but they are not dangerous. Like most garden spiders they eat insects, and they are capable of consuming prey up to 200% of their size. They might bite if grabbed, but other than defense they have no interest in biting humans. Their venom is not regarded as a serious medical problem for humans.
[edit] References
- Rodríguez RL & Gamboa E. 2000. Memory of captured prey in three web spiders (Araneae: Araneidae, Linyphiidae, Tetragnathidae). Animal Cognition 3, 91–97 PDF (Argiope argentata)
- Craig C.L. et. al. (2001). Signal polymorphism in the web-decorating spider Argiope argentata is correlated with reduced survivorship and the presence of stingless bees, its primary prey. Evolution 55(5):986-993. Abstract
[edit] External links
- Diagnostic photographs and descriptions: Argiope trifasciata Creative Commons Licensed
- Diagnostic close-up photographs and descriptions of male and female Argiope aurantia Creative Commons Licensed
- Pictures of Argiope species (free for noncommercial use)
- Picture of Argiope argentata (free for noncommercial use)
- Pictures of A. trifasciata (free for noncommercial use)
- Picture of "A. Bruennichi"
- Death and the Other Side UnSpace Blog Entry and Photos of Argiope Aurantia
