MTPR

Doodlebug Death Traps: A Closer Look At The Infamous Ant Lion

Aug 7, 2019

Ant lions, or "doodlebugs" have impressive mandibles, are adept at camouflage, and are very successful at trapping and ambushing their prey. "Field Notes" takes a closer look at these fascinating insects.

It was a hot summer day—the Fourth of July, to be exact.  My granddaughter Abby and I were on our way to the woodshed.  We were going to need a small fire later to roast our hot dogs and make our s’mores before heading in to Hamilton to watch the fireworks.  As we stepped under the shade of the Ponderosa pines, I saw the tracks.  “Abby, look!  Do you see that?”  As I pointed to the ground, her blank look was my answer.  In the dry, fine, tan soil there were nearly invisible, squiggly marks, like doodles on the ground, and probably twenty-five small, funnel-shaped pits. "Look at the lion tracks,” I told her.  “Oh, Nana,” she chuckled.  “Lion tracks are bigger and look kind of like a big cat tracks.”  “This,” I said, “is a very different kind of lion.”

Ant lion trails, or "doodles".
Credit (CC-BY-NC-SA-2)

Found worldwide in arid and sandy habitats, ant lions belong to the order Neuroptera. Adult ant lions lay their eggs in dry, loose soil. Once hatched, the larvae crawl about in search of a suitable home site, leaving tracks that look like doodles. The same color as the soil, they are well camouflaged. 

Their broad, flattened bodies have short, stubby legs, best for their habit of crawling backwards, which is also aided by the curve of the nearly invisible hairs on their body. As they begin excavation, their oval-shaped abdomen plows through the soil, while their flat heads act like a shovel, flicking sand up and out of the pit. Continuing their backward, downward spiral, abdomen first, the cone-shaped pit is constructed. Once complete, the pit becomes the ant lion’s home for up to three years.

Completely buried now except for its long, piercing mandibles, or jaws, which stick out of the center of the pit, the ant lion larvae lies motionless at the bottom, waiting for its first victim. An ant or a small insect steps inside the rim of the pit and begins the fight for life. The steep sides make it hard to crawl out. The ant lion further confuses the process by flicking particles of sand or dirt onto the frantic insect, aiding its descent into the pit. At some point in the struggle, the insect falls into the bottom of the trap or is impaled by the ant lion’s piercing mandibles. The predator drags its prey deeper into the sand, where it sucks out its body fluids. The ant lion then calmly takes out the trash, flicking the carcass out of its pit, and awaits its next victim.

The larvae develops in stages called instars, digging many pits, some as large as two inches in diameter and depth. The ant lion, now about a half inch in size, pupates in a spherical, sand-covered cocoon for about a month in spring or summer. Upon complete metamorphosis, adult ant lions resemble damsel flies, 1½ inches long, with narrow, net-veined wings they hold over their long, skinny abdomens like pup-tents when they are at rest. Adult ant lions live for one to two months.

Ant lion trap.
Credit (CC-BY-SA-3)

Abby seemed doubtful of my explanation. “Catch one of those ants and drop it into a trap,” I told her. We hovered over an ant lion’s pitfall trap and she released her ant into the center. Tiny sand particles began to move, partly from the ant’s churning legs and partly from the ant lion tossing particles. All the movement happened so fast. Suddenly, the ant lion’s mandible grabbed hold of the ant and pulled it down.

Now that the doodlebug was fed, it was time for us to go build that fire and make our own dinner.

"Field Notes" is produced by the Montana Natural History Center.

(Broadcast: "Field Notes," 7/5/15 and 8/20/19. Listen weekly on the radio, Sundays at 12:55 p.m., Tuesdays at 4:54 p.m. or Fridays at 4:54 p.m.,  or via podcast.)