A Tiny Spider Builds a Spring-Loaded Catapult to Catch Ants
The News
Scientists from Macquarie University in Australia just discovered a brand-new spider deep in the rainforests of Queensland. It's so small you could miss it — but it builds a tiny spring-loaded snare out of silk. When a green tree ant comes by and bites the snare, BOING! — the trap fires the ant up into the spider's web at 15 g's , which is more than the strongest force a jet pilot ever feels. They nicknamed it the "ballista" spider.
"Watch this very carefully," whispered Professor Pip, sliding his crooked spectacles up his nose. He had crouched down in a sunny clearing, and Mia and Leo had crowded close. In his paws, Pip held a long, thin, green twig — and he was slowly bending it into a curve.
"Now, friends — when I let go—"
He let go. TWAAANG! The twig snapped straight, whacking a leaf and showering them with a tiny rain of dust. Both children jumped, then burst into giggles.
"It zoomed!" cried Mia.
"Indeed it did," said Pip. "But here's the wonderful question — where was that zoom hiding the whole time I was holding the twig still?"
Leo thought. "Inside the bent part?"
"Curiouser and curiouser, exactly right." Pip's tail flicked. "When you bend something springy, you sneak energy into it. The twig wants to be straight — and the bending stores up all that 'wanting.' The moment you let go… the wanting becomes motion. We call that elastic potential energy. Elastic like a rubber band, potential meaning it's stored up and waiting."
"That's so cool," Mia whispered.
"Now — far, far away in an Australian rainforest," Pip said, lowering his voice as if telling a secret, "there is a spider smaller than your fingernail. And this spider has invented something. It spends hours every night spinning silk into a careful cone shape, with the lines pulled tighter and tighter and tighter — just like my twig. All that 'wanting' is hidden inside the silk."
"And then?" Leo asked.
"And then it waits. A big green tree ant marches by. The ant bites the silk… and BOING! The whole snare un-bends at once. That ant goes flying up into the spider's web at 15 g's." Pip's tail puffed up. "That is fifteen times the strongest force a jet pilot ever feels in their seat!"
"Like a slingshot!" said Leo.
"Precisely! And here's the most curious part: this spider only catches one kind of ant — green tree ants. Probably because those ants travel in big angry crowds, so the spider has to pick them off one at a time, very safely, very precisely."
Pip looked up into the tree canopy. "All that engineering… in a creature smaller than your fingernail." He pulled out three rubber bands and handed them to the children. "Now you go try."
Spark a Conversation
- What other animals you know of use springs or stored-up energy? (Hint: think about a flea, or a grasshopper.)
- Why do you think the spider only wants to catch one kind of ant?
- If you were going to build a tiny machine, what would it do?