Wednesday, November 25, 2009
Redback Spiders 26/11/09
A new report indicates that Japan is being overun by Aussie redback spiders. Believed to have been introduced years ago in imported cargo, the spiders have bred prolifically and have spread throughout the country. Over a dozen people have reportedly been bitten in the Osaka area alone. The redback spider is a smallish black spider with distintive red markings on the back. A very similar spider, the katapo, lives in coastal areas of New Zealand.
Monday, November 16, 2009
Spiders 12/11/09
Spiders
The world's biggest web-weaving spider has been recently discovered in South Africa. The female of the new species of golden orb weaver spider has a leg span of 13cm -- many times the leg span of the tiny male. Only the females are giants with a body length of 1.5 inches (3.8 centimeters) and a leg span of 4-5 inches (10-12 centimeters); the males are tiny by comparison.
More than 41,000 spider species are known to science with about 400-500 new species added each year. But for some well-known groups, such as the giant golden orb weavers, the last valid described species dates back to the 19th century.
Nephila spiders are renowned for being the largest web-spinning spiders. They make the largest orb webs, which often exceed 3 feet (1 meter) in diameter. They are also model organisms for the study of extreme sexual size dimorphism and sexual biology.*
The world's biggest web-weaving spider has been recently discovered in South Africa. The female of the new species of golden orb weaver spider has a leg span of 13cm -- many times the leg span of the tiny male. Only the females are giants with a body length of 1.5 inches (3.8 centimeters) and a leg span of 4-5 inches (10-12 centimeters); the males are tiny by comparison.
More than 41,000 spider species are known to science with about 400-500 new species added each year. But for some well-known groups, such as the giant golden orb weavers, the last valid described species dates back to the 19th century.
Nephila spiders are renowned for being the largest web-spinning spiders. They make the largest orb webs, which often exceed 3 feet (1 meter) in diameter. They are also model organisms for the study of extreme sexual size dimorphism and sexual biology.*
Monday, November 2, 2009
Redbacks Spiders
New research has showmn that redback spiders eat male mates who do not spend enough time on foreplay. To keep cranky females happy, their partners have to spend about 100 minutes on courtship, doing things such as vibrating their webs and rubbing their tummies. But once the fickle babes are brought to a peak of amorous and receptive behaviour, they will let a stray male mate with them even if he hasn't done any courting at all. If he's quick, he can do the business and then run off before she gets a chance to eat him.
Research at the University of Toronto, in Canada, found Australian redbacks chose males based on a courtship duration threshold. If the first male did not spend enough time wooing the female, she would eat him before he had a chance to mate. But they found that once the female's courtship demands were met, other males could take advantage of the efforts of the first male. The scientists think their work may have clarified why clusters of males are seen around some females when other females remain uncontested.
Research at the University of Toronto, in Canada, found Australian redbacks chose males based on a courtship duration threshold. If the first male did not spend enough time wooing the female, she would eat him before he had a chance to mate. But they found that once the female's courtship demands were met, other males could take advantage of the efforts of the first male. The scientists think their work may have clarified why clusters of males are seen around some females when other females remain uncontested.
Redback Revenge
New research has shown that redback spiders eat male mates who do not spend enough time on foreplay. To keep cranky females happy, their partners have to spend about 100 minutes on courtship, doing things such as vibrating their webs and rubbing their tummies. But once the fickle babes are brought to a peak of amorous and receptive behaviour, they will let a stray male mate with them even if he hasn't done any courting at all.
If he's quick, he can do the business and then run off before she gets a chance to eat him. Research at the University of Toronto, in Canada, found Australian redbacks chose males based on a courtship duration threshold. If the first male did not spend enough time wooing the female, she would eat him before he had a chance to mate.
But they found that once the female's courtship demands were met, other males could take advantage of the efforts of the first male. The scientists think their work may have clarified why clusters of males are seen around some females when other females remain uncontested.
If he's quick, he can do the business and then run off before she gets a chance to eat him. Research at the University of Toronto, in Canada, found Australian redbacks chose males based on a courtship duration threshold. If the first male did not spend enough time wooing the female, she would eat him before he had a chance to mate.
But they found that once the female's courtship demands were met, other males could take advantage of the efforts of the first male. The scientists think their work may have clarified why clusters of males are seen around some females when other females remain uncontested.
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