Animals

Ants Leave Building Instructions for Other Ants

The insects use a pheromone that attracts other ants and prompts subsequent moves in the construction process.

Ants add to their nest-building material a pheromone that attracts other ants and prompts subsequent moves in the construction process.

That was the finding of multi-institutional research out of France that sought to learn more about how it is that thousands of ants, with no guiding central authority, are able to coordinate among themselves to build what are often extremely complex nest structures.

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The researchers studied the nest construction of black garden ants (Lasius niger).

The nests these insects build are a network of underground galleries as well as above-ground mounds containing interconnected chambers. The ants create the chambers by building pillars around them (see photo below).

Shown are regularly spaced pillars and walls built under experimental conditions by groups of 500 ants of the species | Guy Theraulaz / CRCA / CNRS (Toulouse)

The scientists observed that two key, indirect interactions governed the nest-building activity.

First, chemistry played a role. Ants tended to lay building materials atop other material left in the same place, as opposed to putting them in another, new spot. What told them to build upon previous work? It turns out, the scientists learned, the ants were adding a pheromone to the building material, leaving behind a chemical signal other ants used to build atop the same spot and, thus, build the individual pillars.

Second, the ants took their cues for the physical size of the pillars by using their own body dimensions. Whenever a pillar grew as high as a typical ant's body length, the little builders knew it was time put a cap on that pillar and begin building laterally the next section.

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The researchers say the lifetime of the pheromone - how quickly it breaks down and loses its "power" over the ants - was dependent upon climate and that different climates resulted in different nest structures.

In drier environments, the pheromone broke down faster, which resulted in fewer pillars being built and, therefore, roomier chambers that could fit more ants, the better to conserve humidity.

But in more humid environments, the team found, the pheromone lasted longer, resulting in more pillars and smaller chambers.

The researchers -- comprised of scientists from CNRS, Université Toulouse III – Paul Sabatier and Université de Nantes -- published its findings in the January 18 issue of PNAS.

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Insects and other creepy crawlies may be tiny, but their lineages are mighty, finds a new study that determined the common ancestor of mites and insects existed about 570 million years ago. The study, published in the latest issue of the journal Science, presents an evolutionary timeline that settles many longstanding uncertainties about insects and related species. It found that true insects first emerged about 479 million years ago, long before dinosaurs first walked the Earth. Co-author Karl Kjer, a Rutgers entomologist, explained that mites are arthropods, a group that's distantly related to insects. Spiders and crustaceans are also arthropods.

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Spiders such as the huntsman spider can, like mites, trace their lineages back to about 570 million years ago, according to the new study. The researchers believe that the common ancestor of mites, spiders and insects was a water-dweller.

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Millipedes, such as the one shown here, as well as centipedes are known as myriapods. The most recent common ancestor of myriapods and crustaceans lived about 550 million years ago. Again, this "mother of many bugs" would have been a marine dweller. Kjer explained, "You can't really expect anything to live on land without plants, and plants and insects colonized land at about the same time, around 480 million years ago. So any date before that is a sea creature." Moving forward in time, the most common ancestor of millipedes and centipedes existed a little over 400 million years ago. The leggy body plan has proven to be extremely successful.

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"This is an early insect that evolved before insects had wings," Kjer said. Its ancestry goes back about 420 million years. The common ancestor of silverfish living today first emerged about 250 million years ago. Dinosaurs and the earliest mammals likely would have then seen silverfish very similar to the ones that are alive now.

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Dragonflies and damselflies have family histories that go back about 406 million years. Kjer said that such insects looked differently then, however. "For example," he said, "they had visible antennae." Their distant ancestors were among the first animals on earth to fly.

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"Parasitic lice are interesting, because they probably needed either feathers or fur," Kjer said. As a result, they are the relative newbies to this list. Nonetheless, the researchers believe it is possible that ancestors of today's lice were around 120 million years ago, possibly living off of dinosaurs and other creatures then.

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Crickets, katydids and grasshoppers had a common ancestor that lived just over 200 million years ago, and a stem lineage that goes back even further to 248 million years ago. A trivia question might be: Which came first, these insects or grass? The insects predate the grass that they now often thrive in.

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Dinosaur Era fossils sometimes include what researchers call "roachoids," or wing impressions that were made by ancestors to today's roaches, mantids (like the praying mantis) and termites. "Some cockroaches are actually more closely related to termites than they are to other cockroaches," Kjer said, explaining that this makes tracing back their lineages somewhat confusing. He and his colleagues determined that the stem lineage goes back about 230 million years, while the earliest actual cockroach first emerged around 170 million years ago.

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Termites and cockroaches have a tightly interwoven family history. Termites similar to the ones we know today were around 138 million years ago. Now we often think of termites as pests, but they are good eats for many different animals, which back in the day would have included our primate ancestors.

Flies like houseflies that often buzz around homes belong to the order Diptera, which has a family tree that goes back 243 million years ago. The most recent common ancestor for modern flies lived about 158 million years ago, according to the study. There is little doubt that the earliest humans, and their primate predecessors, had to contend with pesky flies and all of the other insects mentioned on this list. All of these organisms are extremely hardy. The researchers determined that, in the history of our planet, there has only been one mass extinction event that had much impact on insects. It occurred 252 million years ago (the Permian mass extinction), and even it set the stage for the emergence of flies, cockroaches, termites and numerous other creepy crawlies.

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