Researchers Stage Epic Spider-Worm Duels In The Name Of Science

A harvestman spider (Bruce MacQuee/Shutterstock) and a Cephaloflexa predatory flatworm (Wikimedia Commons)

Each night on the tropical forest floors of Brazil, predatory flatworms prowl for the unlucky small invertebrates that will become their next meal. Using their dexterous, muscular bodies and a glue-like mucus, the worms capture and immobilize their prey. They then either swallow the organism whole or dissolve its tissues with throat secretions (the mouth is located in the middle of the body and can turn inside out) and slurp up the mess.

One of the worm’s preferred targets are harvestmen spiders, an order of arachnids often referred to as daddy longlegs. However, because these spiders are formidable in their own right – thanks to their sharp leg spines, reinforced exoskeletons, unpalatable defensive chemical secretions, and mouth pincers – biologists at the University of São Paulo were keenly curious to observe exactly what goes down during these moonlit struggles for survival.


“In nature, we have repeatedly found the species C. bergi feeding on nocturnal harvestmen and wondered how these delicate animals manage to capture, if ever, these armored arachnids,” the team wrote in the Journal of Zoology.

So naturally, they set up a series of 32 one-on-one miniature matches between Cephaloflexa bergi flatworms and harvestmen of the species Mischonyx cuspidatus. The chosen arena? A Tupperware dish.

A bit like playing multiple rounds of Mortal Combat, the sequence of fights revealed the strengths and weaknesses of each creature. In 22 instances, the flatworm attacked the harvestman, each one initiating with a fast strike of their sticky head; which once landed on a spider body part, dragged the spider toward itself.

“Throughout the process the flatworm released mucus onto the harvestman, gluing its legs [to] each other and the body to the arena, hampering harvestmen’s movement.”


Five of the 22 attacked spiders were able to escape before the 10-minute timer ran out, the other 17 were firmly pinned in place and their body contents gobbled up. Yet before their ultimate death or evasion, 15 of the 22 spiders managed to chop the worm with their leg spines. Two of these crafty spiders (both of whom escaped) actually cut the worm in half using this method. Another 15 released their chemical defenses, which, at least temporarily, forced the worm to flee. There was only one case where a harvestman pinched a worm with its mouthparts; the worm quickly moved away.

Obviously pleased with the insights gained, the authors conclude that their study “highlights the importance of examining the natural interactions between prey and their actual predators, in contrast to artificial stimuli or simulated predators.”

Not to mention that the resulting video footage is nail-biting drama gold.


  • tag
  • Arachnid,

  • nature,

  • food chain,

  • tropical,

  • rainforest,

  • predation,

  • ecology,

  • jungle