Posted by: Rob Viens | June 13, 2012

Red-Hot with Spiders in Rio II: Jumping Spiders

June 13th brought more socializing for Darwin. It is interesting to see all the friends he is making in Rio:

“Dined with Mr Cairnes; who is the only merchant whom I have met with in society.— The generality are little above shopkeepers. I spent an agreeable evening.— Mr Price, a merchant from round the Horn & a passenger with Capt Waldegrave, gave a great deal of amusing & interesting information about the plains or what we better designate these the horse & cattle breeding countries.— Mr Price married a Spanish lady who is since dead & has with him his two little daughters, Carlotta & Theresa; the Signoritas can speak nothing but Spanish; very pretty, & their motions most exceeding graceful; Theresa, the least about 8 years old, could not help dancing when she heard music, & with a rose in each hand as her partner, danced most exquisitely.” (June 13)

“Capt Waldegrave” was almost certainly Captain Granville Waldegrave, 2nd Baron of Radstock.  The Captain was the son of William Waldergrave (not surprisingly the 1st Baron of Radstock), who had been the Governor of Newfoundland in the late 1700’s. Granville was a Royal Navy man his whole life and died in 1857 with the rank of Vice Admiral. From 1837 to 1841 he was the personal naval assistant (aide-de-camp) to Queen Victoria. From what I can tell, the rest of the merchants and little girls are lost to history – with only a first or last name, they are impossible for me to find.

Speaking of dancing – how about those jumping spiders…Darwin mentions them briefly in his notebook (though doesn’t get the family name exactly right):

“In the Saltigrades the typical genus Salticus is almost infinite in species.— In sweeping amongst herbage nearly as many spiders as Coleoptera are taken, especially of this last family.” (Zoological Notebook)

In the world of predatory spiders, jumping spiders (spiders of the family Salticidae)  are the big cats.  They have good vision, stalk their prey, then quickly pounce on them for the kill. Of course, unlike cats, jumping spiders can use silk to swing across a large gap or to build a “pup tent” for sleeping in, but hey, no analogy is perfect.

Phidippus mystaceus (by Thomas Shanon)

Phidippus mystaceus

There are over 5000 species of jumping spiders found across the globe – having adapted to warm and cold climates , as well as wet and dry conditions.  It has been suggested that one jumping spider (Euophrys omnisuperstes) holds the record for the highest permanent resident on Earth – living at 6,700 m on Mt. Everest. At 514 species (to date, according to http://www.jumping-spiders.com), Brazil has more jumping spider species than any other country in the world.

North American jumping spider species (from tulsamastergardeners.org):

Jumping spider

One of the most distinguishing characteristics of these spiders is their eyes.  Salticidae frequently have 4 pairs of eyes around the front and sides of the head.  The four larger front eyes tend to stand out and make these spiders look like little aliens.  These eyes give jumping spiders some of the best eyesight in the invertebrate world.  Not only is their field of vision excellent, but the front eyes allow for fairly clear vision and depth perception (without which, pouncing on prey would be a lot more hit or miss (literally)).

Field of view of a jumping spider (from Wikipedia Commons)

Jumping spider field of view

Jumping spider species (by Nick Hobgood)

Jumping spider

Because if their excellent eyesight, visual clues such as color or movement play an important role in mate selection for jumping spiders. Courtship frequently requires the male to do an elaborate “dance” to win the affection of the female.  This is what Darwin would later refer to as sexual selection – a form of natural selection where one sex (the female in this case) selects for characteristics in a mate.  Since it is primarily only the males that are selected that are able to reproduce, the characteristics that are selected for are passed down to offspring.  Thus the population evolves to favor colorful males and/or those considered “good dancers”.  This is almost certainly why the jumping spiders are some of the most colorful and ornate spiders in the world. (In the vertebrates this characteristic is most pronounced in birds – with one of the best known examples being the elaborate tail of the peacock.)

Some truly stunning pictures have been collected on the artist En Derin’s website including this one by Thomas Shanon:

Jumping spider

Sweet spider dreams! (RJV)

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Responses

  1. My desire to have a prehensile tail for a day has been consistent for decades. Much as I’d like to experience being a cat, small or large, or a bird, it’s been the prehensile tail that most held my fascination. Now, unexpectedly, comes a competitor…. to be a jumping spider with all that range of vision. Tail? Eyes in the back of my head? Swing from trees? Or jump 20 times my body size? Tail? Eight eyes? True dilemma.


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