This Beetle Pretends to be an Ant's Butt

A newly-discovered species of beetle manages to benefit from army ants by riding around on them. Nymphister kronaueri is a small red beetle that clamps its jaws around the waist of the army ant Eciton burchellii and tags along, unseen because it looks like the ant's normal backside. Science writer Ed Yong calls it "A prosthetic posterior. A gluteus extraneous. A beetlebum." Christoph von Beeren and Daniel Kronauer discovered the beetle in 2014 in Costa Rica while following the relentless army ants.  

Von Beeren and Kronauer were also relentless. They would watch the ants for hours at a time, sitting in fold-up chairs in the pitch-black jungle, and peering at the legions through headlights.  One day in the spring of 2014, they realized that some of the ants looked a little odd. “The abdomens reflected the light differently, and the color was a little different,” says von Beeren. “Then, we noticed that they looked like they have two abdomens.”
They collected some of these dual-derriered insects and put them in a vial. Back at camp, Kronauer shook the vial… and the back-up backside fell off. It was a beetle. “And it blew our minds,” says von Beeren. After working with USDA entomologist Alexey Tishechkin, he realized that the bonus-butt beetle was new to science. And he named it Nymphister kronaueri, after his colleague Kronauer, who helped to discover it.

Not much is known yet about the beetle. Does it benefit by hiding in plain sight? Does it eat what the ants eat? Read what we do know about the butt beetle at The Atlantic. -via Metafilter