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Army ants observed in Costa Rica at first appeared to have a duplicate body part. But of the two oval structures visible at the ant’s back end, the upper one actually is a symbiont, a beetle hitching a ride on the ant.

Beetle behinds, flamingo friendships, and other wonders

These novel research findings range from a fly’s brain and an ant’s rear end to the footsteps of human ancestors and the bonds among flamingos.

This story appears in the September 2020 issue of National Geographic magazine.

This army ant bears a beetle behind

When colonies of hundreds of thousands of army ants go on the march, with them go symbionts that sponge off the army’s resources—and members. One symbiont found in Costa Rica was hiding in plain sight: a beetle that clamps its mandibles around the ant’s middle and rides along, looking like a double-vision version of the ant’s backside. —Patricia Edmonds

Flamingos make friends

The avian world’s pink-feathered icons form long-lasting, loyal friendships, scientists recently discovered. The flamingo bonds vary, from mated couples that build nests and raise chicks each year to same-sex friends or groups of three to six close buddies. The relationships, characterized by standing close together, may last decades. Like humans, flamingos befriend those they get along with and avoid those that cause squabbles. —Virginia Morell

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Researchers studied the relationship behaviors of Caribbean flamingos, seen here, and four other flamingo species.

Walking back in time, in a volcano’s shadow

Nine miles north of the volcano called Ol Doinyo Lengai, which means “mountain of God,” researchers funded by the National Geographic Society have cataloged a rare find: more than 400 fossil footprints laid down by humans who walked and jogged across mudflats 10,000 to 19,000 years ago. Discovered along the shore of Tanzania’s Lake Natron by local villager Kongo Sakkae, the Engare Sero site lets scientists “really start to see social behavioral patterns in our Homo sapiens ancestors,” says team leader Cynthia Liutkus-Pierce, a geologist at Appalachian State University. One set of tracks reveals 17 people walking toward the southwest, 14 of whom were probably adult women. That suggests a female-led foraging party, a division of labor used by some modern hunter-gatherers. To save Engare Sero’s trackways from erosion, researchers have 3D-scanned them and are partnering with local officials to build a protective enclosure and workstation. In the meantime, Sakkae walks to Engare Sero from his village every day at sunrise, keeping a watchful eye on the footprints he found. —Michael Greshko

A brain circuitry map worth buzzing about

This bundle of about 600 fruit fly neurons, colored for contrast, allows a fly to integrate and act on information that its senses gather. Scientists from the Janelia Research Campus and Google have so far mapped about a third of the fly brain, 25,000 nerve cells that form some 20 million connections. The ultimate goal: To map the whole brain and key nerves, to learn more about how the organ’s areas are linked. —Theresa Machemer

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Fly brain in detail

This portion of a fruit fly’s brain, some 600 neurons, enables the insect to integrate and act on information gathered by its senses.