More Than You Probably Ever Wanted to Know About Spiders

I somehow missed that March 14 was “National Save a Spider Day.”  (And you probably thought it was “Pi Day.”)  Fortunately, a recent scientific paper gives me a belated excuse to blog about our arachnid friends.

Researchers in Europe have published a comprehensive study of the world’s spider population.  Among the report’s highlights:

  • Scientists have identified more than 45,000 different species of spiders around the world.
  • The average global density of spiders is 131 individuals per square meter. In some areas, they can reach a peak density of 1,000 individuals per square meter.
  • All spiders are carnivorous, meaning that they eat meat.
  • The total global spider population weighs 29 million tons.
  • This global spider community consumes an estimated 400-800 million tons of prey every year.

As the Washington Post noted in a summary article, “Spiders could theoretically eat every human on Earth in one year.”  Think about that for a moment.

Of course, Agilent technologies and solutions are used to study spiders.

U.S. scientists noted that Virginia songbirds were being contaminated by aquatic mercury.  One theory was that the mercury was accumulating in mayflies born in the river sediment.  Mayflies were being eaten by spiders, which in turn were being eaten by songbirds.

But using an Agilent electrophoresis system, the scientists found no traces of mayfly DNA in wolf spiders during the mayfly emergence season.  They concluded that the songbirds are more likely getting mercury directly from the floodplain soil where they nest.

Researchers at Georgetown University noted that a particular spider (Peckhamia picata) is able to mimic an ant, both physically and behaviorally.  This enables it to evade two different predators: spider-hunting wasps and predatory jumping spiders.

The Peckhamia picata spider (figure 21) resembles an ant.  (Graphic from wikimedia commons)

The peckhamia picata spider (figure 21) resembles an ant. (Graphic from wikimedia commons)


Using an Agilent gas chromatograph, mass selective detector and software, the researchers analyzed the chemicals emitted by the spider.  They discovered that not only does the spider visually resemble an ant, it actually emits chemicals that further convince enemies it is an ant.

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