You've likely come across a daddy longlegs in the garden, and odds are good you've seen one that was missing one or more of its eight legs. How did the limb go missing, you wonder. Believe it or not, the arachnid may have dropped it on purpose.
Daddy longlegs can willingly drop a limb to escape a predator. KQED Science reports, "Daddy longlegs’ appendages don’t need to be pulled off because these arachnids, related to spiders, drop them deliberately. A gentle pinch is enough to trigger an internal system that discharges the leg. It’s a way to stay alive in the wild if something is trying to devour the bug’s limb. Whether it hurts is up for debate, but most scientists think not, given the automatic nature of the defense mechanism. The only blood lost comes from the detached leg."
It's certainly less painful than being eaten. The process is called autotomy, and it's of particular interest to entomology researcher Ignacio Escalante of the Elias Lab at UC Berkeley. Escalante is researching how the limb loss affects long-term survival. One thing is certain: It affects long-term stride. When a daddy longlegs loses a leg, it needs to adopt a new stride that allows it to walk effectively with fewer limbs.
KQED Science explains, "After losing one leg, a daddy longlegs begins to favor 'stotting,' where it dribbles its body on the ground like a basketball with every stride. After losing two legs, it turns to 'bobbing,' where the vertical plane of movement becomes pronounced."
It only takes a daddy longlegs a day or two to figure out a new method of locomotion. Interestingly the change in stride also may help it avoid future run-ins with predators since the odd and often bumpy way of walking could make it more difficult for a predator to plan a strike.
Check out this fascinating Deep Look video that explains just how daddy longlegs can ditch a leg to ditch a predator:
But does the loss of a leg or two (or three) affect the arachnid's chances on the dating scene? It's possible. Escalante plans to research mating success for animals that have lost limbs.
Of course, it could also go the other way for amorous arachnids even if they have all eight limbs. “I’ve seen females pop the leg off a male because they don’t want to mate with him,” Kasey Fowler-Finn, who researches daddy longlegs at St. Louis University, told KQED.