Blogs / Discoblog

Are ants taking over the planet? Well, they’ve definitely spread, and they know which ants are on their colonial “team.” In fact, a single colony consisting of billions of Argentine ants, originally natives of South America, have spread onto every continent save Antarctica, thanks to human activity.

Even more remarkable, the insects can tell which ants are from their own colony, even if they live on different continents. When scientists placed ants from the Argentine colony together, even if they were taken from other countries, they were amiable (i.e., nonviolent) to each other. Contrast that with the aggression ants from separate colonies displayed when they came into contact with each other, according to the BBC:

Argentine ants are renowned for forming large colonies, and for becoming a significant pest, attacking native animals and crops. In Europe, one vast colony of Argentine ants is thought to stretch for 6,000km (3,700 miles) along the Mediterranean coast, while another in the US, known as the ‘Californian large’, extends over 900km along the coast of California. A third huge colony exists on the west coast of Japan….

Ants from the smaller super-colonies were always aggressive to one another. So ants from the west coast of Japan fought their rivals from Kobe, while ants from the European super-colony didn’t get on with those from the Iberian colony. But whenever ants from the main European and Californian super-colonies and those from the largest colony in Japan came into contact, they acted as if they were old friends.

Experts say the ants likely are genetically related, so they recognized the chemical composition of each others’ cuticles.
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Good public sanitation is a mark of advanced civilizations. Humans have dealt with the “bathroom problem” mainly by burying, flushing, or otherwise sequestering our waste products in some far off, out-of-sight, out-of-mind location. In this way, we’re similar to mole rats that build specialized “latrine chambers” in their underground habitats. A new paper in Animal Behavior examines alternative ways to handle the sanitation issue, developed by some of the world’s most sophisticated societies: eusocial insects like ants, bees, and wasps. One strategy involves something known as the “blind gut.”

Colonies of eusocial insects can contain millions of individuals. Because dropping feces at will would cause a serious toxic hazard, many species have developed a way of holding it in for a really long time. The youngsters, or larva, of the order hymenoptera, have a “blind gut,” meaning one that does not connect the mouth with the anus. Essentially, this means their waste products are trapped inside their bodies for weeks to months, or the entire duration of the larval stage. Only when they pupate (when the larva changes into the adult form), does their waste get expelled in one big, stinky pellet known as the meconium. In the honeybee, the meconium is expelled during its first flight out of the nest. (Imagine human teenagers holding it all in until right before they leave home for college…) After the meconium is quickly disposed of, the adult insects develop a normal continuous gut.

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Vampirism isn’t just for bats and Edward Cullen anymore. Some ordinary insects are also beginning to covet human blood, sweat, and tears, because these fluids contain valuable salt that is hard to find in their natural environment. Surprisingly, many species are even preferring salt to energy-rich sugar.

The idea that salt attracted bugs first dawned on a team of sweaty scientists studying insects in Peruvian forests. Puzzled by the swarms of tiny bees attacking them, the scientists soon realized that the bees were trying to get a taste of their sweat. Animals need salt to activate nerves and muscles, and to maintain water balance in their cells.

Intrigued, the scientists littered the forest floor with hundreds of vials filled with either sugar or salt and counted the ant species they baited. They found that ant species living within 100 kilometers of the oceans (with easy access to salt) chose sugar over salt. But ant species living farther inland had a noticeable preference for salt. Reporting in the Proceedings of the National Academy of Sciences, the scientists say the salt cravings were only seen in vegetarian ants, since carnivorous ants can get enough salt from the bodies of their prey.

Which brings us to the vampire moths.

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Many ants are known to be slave masters—their raiding parties steal the young from colonies of rival ants and raise the foreigners as workers in their own nest. However, Susanne Foitzik of Ludwig-Maximilians University in Munich may be the first researcher to study an ant slave rebellion.

The rebels are Temnothorax, tiny ants only about the size of the comma in this sentence. Their captors are called Protomognathus americanus, and despite being only a little larger, these bullies enslave the smaller insects. Inside the larger ants’ nest, which is built inside an acorn, the smaller ants are put to work caring for their masters’ young. But sometimes, Temnothorax slaves revolt against their servile existence and slaughter the Protomognathus larvae they’re supposed to be babysitting, as well as some of the enemy workers.

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Earlier this month we wrote about a study of adaptable ants that changed their leaf-gathering strategies to bypass a roadblock thrown in their way. These clever insects solve traffic jams much more easily than big-brained humans do, and now scientists want to borrow their secrets to ease our highway woes.

Ants leave a trail of pheromones to show others the best way back to the nest; when others follow, they leave their own pheromones and the trail is reinforced. They all work together through what biologists call “distributed intelligence.” You can see this skill demonstrated in a Slate video here.

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Leaf-cutter ants are one of the world’s most organized species, sending out swarms of individuals to cut off leaf scraps and carry them back to the nest. Now, it seems, they’re even smarter than we thought: They can adjust on the fly.

To test the insects’ intelligence, a team of scientists led by Audrey Dussutour at the University of Sydney threw a road block in their way. The researchers built a lab setup in which the ants could only travel between a source of leaves and their nest via a short passageway with a roof only one centimeter off the ground. But instead of getting confused or frustrated that their cargo wouldn’t fit under the bridge, the ants adapted their tactics.

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Who’s the boss? Milkweed is the boss.

Milkweed plants engage in a helpful bit of mutualism with the aphids and ants who take up residence on them. Aphids feed on the milkweed’s sap, then secrete honeydew, which ants eat. The ants, in turn, are the muscle of the operation—they help both the plants and the aphids by fighting off potential predators like caterpillars. The partnership goes three ways, but the power is not equal—milkweed is in control.

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Residents of five counties in the Houston area have found themselves besieged by a most unwanted visitor: A new species of swarming, electronics-killing ants. Normally found in the Southeast and the Caribbean, these reddish-brown arthropods known locally as “crazy rasberry ants” are thought to have arrived in Houston via a cargo ship a few years ago, and have since spread in droves. Over-the-counter bug sprays can’t touch them, and they’re liable to bite—though not with the painful stinger of that other Texas staple, fire ants, whom the crazy raspberries eat for lunch (literally).

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