When These Arachnids do Battle, the Winner is Never Certain

When a quick but unprotected warrior does battle with a well-armored and stronger foe, the winner usually seems certain. There's a reason that armored knights were considered champions of the battlefield in medieval times. Still, when it comes to clashing arachnids, things could prove a little different.

According to a study recently published in the journal Animal Behavior, precision kill strikes are everything for the recluse spider. Small-but deadly, most recluse spiders have exceptionally sharp and poisonous fangs. However, like most spiders, they are fragile things, with spindly legs easily damage by stronger foes.

In numerous field surveys, researchers have observed recluse spiders attacking and eating harvestmen, also commonly known as "daddy-longlegs" (Mitostoma chrysomelas). Not to be confused with the spindly basement-dwelling daddy-longlegs spider (Holocnemus pluchei), harvestmen do not have the characteristic eight eyes and two body segments of normal spiders. Instead, they are one solid mass of armor with eight legs. Master hunters in their own right, harvestmen are generally stronger than even large spiders, and are adept at catching even the most slippery prey.

It's strange then that spiders, usually about the same size as harvestmen, would chose them as their prey. And yet that's exactly why, researchers suspect, harvestmen boast their impressive armored bodies.

Researcher Rodirgo Willemart from the University of São Paulo, Brazil recently spent time watching this intriguing predation in action. (Scroll to read on...)

"Usually both fangs slide on the surface of the harvestman's body," he explained to New Scientist, adding that the result becomes more of a battle than your average predator-prey scenario.

Interestingly, this doesn't always happen. Willemart and his team found numerous  carcasses of harvestmen in the webs of recluse spiders in Brazil. The successful spider were then brought to a lab, where  they were introduced to more harvestmen prey. A stunning 31 out of 38 spiders found a way to kill and then eat these harvestmen, revealing the trick to a successful hunt.

"Recluse spiders are exceptional in that they do not try to pierce through the armor. They simply avoid it and bite the soft parts of the harvestman," he explained.

According to the study, the research team observed the successful spiders actually feeling around the harvestman's body even as they grappled. When the recluse finally found an unarmored portion, no matter how small, it lunged with frightening speed and accuracy, plunging a venomous fang into its prey.

Still, there are many questions to be asked, especially concerning why only some spiders know to do this. Is it a learned behavior or are some spiders simply better at it than others? A lot more research will be needed to find out.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).