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Monday, November 20, 2017

Why jumping spiders are awesome

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  • With eight eyes positioned around their "head" (cephalothorax, really), jumping spiders have almost 360 degree vision - they live in a panoramic world.


  • They are capable of learning and problem-solving: jumping spiders of the genus Portia, when hunting web-building spiders, will try to mimic the vibrations of a struggling insect or a male suitor until they find a successful technique. Even if the web-building species is one unfamiliar to Portia (or even its ancestors ), by trial and error it will decipher and remember the successful vibration pattern.

 

  • They are the largest family of spiders (~5000 species).


  • Bagheera kiplingi, a jumping spider from Central America, is the only known spider that is predominantly vegetarian. They eat Beltian bodies, small protein and fat-rich buds which grow on the leaf-tips of certain acacia trees. Many other species consume nectar, as part of a healthy (spider) diet.

 

  • Using internal hydraulic pressure, they can jump between 43 and 60 times their body length – with a bungee cord attached. The silk they trail behind them when they leap allows them to recover if they miss their target, and may aid in stabilising their motion through the air.

 

  • Some species have tetrachromatic vision (four different retinal cone receptor types) – humans (lame) only have three (trichromatic). This means the jumping spider's ability to differentiate colours is probably better than ours. In addition, their visible spectrum extends into the UV range.

 

  • The retina of the main anterior lateral eyes (the two massive front ones) can swivel to view off-axis objects. This rapid movement can be seen within the spider's eye if you look (very) closely!

 

  • They are the only spiders which will attack motionless (or dead) prey. Presumably, they can visually interpret the shape of a suitable meal, even if it isn't moving.

 

  • They have both book-lungs (old-school spider technology) and a well-developed tracheal system to cope with their high metabolic needs.

 

  • They use triangular-shaped setules (tiny hairs-on-hairs) to hold on to apparently smooth surfaces. The setules rely on van der Waals force (close-proximity molecular attraction) that exists at distances of 1nM or less. If all the setules were in contact with a surface at once, the spider could support 170 times its own bodyweight.

 

  • They dance! If you don't believe me, watch this video.

 

 

  • When two males are competing for one female, they will have a dance-off with the loser retreating in defeat (and presumably to brush-up for next time).

 

  • They are extremely curious and will interact with humans. I had one who sat on my printer and watched me for three days as I worked on the computer. One the fourth day, I found it dead next to the keyboard. It could have wandered off any time it wanted (they can climb up slippery bathtubs, after all), but it didn't. Maybe it thought that I was a suitable mate, and it died from a broken heart (spiders do have a heart – it's on the dorsal side of their abdomen).