BY CONSTANCE CASEY
Dedicated and patient arachnologists identified two more species of peacock spider this year. Most of us have never heard of these creatures, but the more the better. They are creatures with whom it’s a pleasure to share the world. Not because they eat flies, though that’s a service much appreciated in their native Australia, but because the male performs an intricate dance with an iridescent fan raised over his body. The performance, which includes percussion with his feet, is all the more impressive because a septet of these showy spiders could fit on a man’s thumbnail. A male peacock spider is four millimeters long; that’s about one sixth of an inch.
The two new spider species add to the 40 or so in the genus Maratus, part of the family Salticidae—jumping spiders. There is Maratus skeletus, named for the bold white markings on the male’s black body. It’s dramatic, but the charmer is Maratus jactatus, nicknamed “Sparklemuffin” by the University of California, Berkeley graduate student Madeline Girard, whose paper in the journal Cell describes its astounding courtship dance.
“Sparklemuffin” spiders have so far been collected only in the Wondul Range National Park in Queensland. Not surprisingly few people have seen the spiders’ display in the arthropod-ic flesh. The hopeful male first extends his furry-looking spinnerets in a sort of disco, or flamenco, move as he dances from side to side. If the desired female responds, he hoists the shiny flaps over his abdomen. They do look amazingly like a peacock’s fan—iridescent blue scales with bands of red and orange.
He goes on sidestepping jauntily, tipping his glimmering display and, in a sense, singing. The drumming of his feet, vibrations the female picks up, also indicates something significant to her. Musical sense? Strength? There could be a message as complicated as the one a bee’s dance communicates.
The peacock spiders are part of the family of jumping spiders, Salticidae, the largest of the spider families with 5,000 species around the world. Jumping spiders don’t spin webs; they stalk and pounce on their insect prey.
Because they’re hunters rather than patient web minders, jumping spiders have evolved to see in remarkably high resolution. Happily, the female peacock spider, herself drab as a peahen, is capable of appreciating not only the choreography of the courting male but also his colorful costume. Peacock spiders are equipped with eight eyes—a front row of four looks forward. Some of the eyes detect motion; some give the spider a wide-angle view. It was recently found that one set of specialized eyes can see a broader spectrum of colors than human beings can. The spiders’ eyes are sensitive to ultraviolet light as well as to the spectrum visible to us.
The male’s display obviously is intended to seduce as many females as possible. Its elaborateness raises many beguiling questions. How did the dance evolve? What is the female looking for? What qualities make a male a winner? The eggs that result from successful pairing produce hatchlings that look very similar to adults. Could there be a tiny male somewhere in the outback practicing his show?
Constance Casey, a former New York City Parks Department gardener, is a contributing editor to LAM.
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