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Jump, Thump

All spiders make silk. For many spiders, silk is about building someplace to stay still. But for jumping spiders, it's about having the freedom to move around. Fast.

Jumping spiders make up the family Salticidae. This is the biggest spider family, numbering about 5,000 species. No matter where you live, you've probably come across a jumping spider one time or another in your home. They're usually compact, and because they're diurnal, you may find them traveling across the kitchen table or a windowsill or wall in broad daylight. (Also, it has to be said: magnified, they're quite quaint. There's something about those big, forward-facing eyes and fuzzy chelicerae that evoke King George V on a bad hair day.) Don't torment it, but it's really fun to nudge a jumping spider from behind and watch it spring away. Even more fun is to watch one jump perpendicularly away from a wall and then seemingly defy gravity as it lands back on the wall a few inches down.

You have to look closely to see the secret behind this daredeviltry. Salticids belong to the spider infraorder Araneomorphae, all of whose members produce major ampullate, or dragline silk. All araneomorphs can dangle on major ampullate silk threads. In fact, it's likely major ampullate silk evolved because stronger silk allowed more spiders to drop out of the way of danger. Salticids just took this innovation and leapt with it. This super-strong silk lets them recover from any jumps they might miss: it reels out from their spinnerets as a safety line as they travel through the air.

We're only beginning to understand how much we don't see and don't hear and otherwise don't sense what's going on in the miniature world of the jumping spiders. I was reminded again of how much sheer imagination and creativity are involved in experimentation--qualities often masked by the dry prose of scientific papers--when I recently came across this amazing PBS film about Damian Elias's research on jumping spider courtship. Enjoy:

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