A Tiny Spider’s Secret to Taking Down Big Prey

Image credit: 
Pekar, et al.

At first glance, the pinhead-sized spider Zodarion cyrenaicum seems like it's on a suicide mission every time it hunts for a meal. Its preferred prey is a desert ant, Messor arenarius, some three times bigger and six times heavier than itself. But as David and the Red Viper have shown us, size isn’t everything—especially if you’ve got some slick moves and the right tools for the job. 

Wondering how the spiders consistently come out on top when battling the relatively-giant ants, Czech scientists watched some captured critters hunt in their lab. 

They found that both adult female and juvenile spiders rely on a potent venom that can immobilize an ant with just one bite. They use slightly different tactics to stay out of harm’s way until the venom does its job, though. (The adult males don’t hunt at all, and instead take a cut of the food from a female's or juvenile’s kill).

The adult female spiders attack quickly from behind, biting the ant’s abdomen or hind leg, and then retreat from any counter-attacks until the ant falls.

Following a bite, the ant stopped moving and stood still with opened mandibles,” the researchers write. “Meanwhile, the bitten limb contracted, and the gaster [the bulbous hind end of the ant body] bent under the thorax. Such a C-shaped position lasted for several minutes; then the ant collapsed, falling on one side. At this moment, the spiders approached and began to feed.”

The juvenile spiders are small enough that they can take a different approach. They actually climb onto their foe, deliver a bite to the abdomen, and then hang on to the ant’s back until it’s paralyzed so it can’t retaliate. Even at a young age, their venom is already something to be reckoned with. While the venom glands of an adult are more then 50 times bigger than a juvenile’s, the younger spider’s venom only takes a little bit longer to immobilize the prey. 

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July 8, 2014 - 1:00pm
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