Pit-building antlions: Nature’s sand trap killers

If you’ve ever seen small, cone-shaped pits in fine soil or sand, you’ve likely found an antlion trap.

These pit-building insect larvae hide beneath the surface, waiting to ambush ants and other small insects that fall in. When the prey is within reach, antlions use massive jaws and a paralyzing toxin to overpower it.

“They have mandibles that are ridiculously massive, and they are ferocious predators,” said Wizzie Brown, Texas A&M AgriLife Extension Service entomologist in the Texas A&M College of Agriculture and Life Sciences Department of Entomology, Austin. “Once antlions get hold of their prey, it’s over.”

What is an antlion?

Brown clarified that some species of antlions, also known as doodlebugs, don’t use pitfall traps to hunt. But in their larval stage all these tiny predators are terrifying to their prey, which include ants and other small insects.

While antlion larvae are found in pits, adults resemble damselflies but are closely related to lacewings. Like lacewings, which typically fly around sundown, are attracted to lights and feed on nectar, the antlion is considered a beneficial insect.

“Some antlions just move around in the dirt, dragging the tip of their abdomen and leaving a doodling pattern, which is where the name doodlebug comes from,” Brown said. “But the ones that do dig pits are super cool to see in action.”

Where do antlions live?

Antlion larvae can be found in any areas suitable for burrowing or building pits.

Brown said pit-building antlions live in areas with sandy, loose soil throughout the U.S. They prefer locations sheltered from rain and wind, such as the base of trees or around buildings.

What do antlions look like?

Antlions have several distinctive features that make them easy to identify.

Some key features of antlion larvae:

• Size – Up to one-half to three-quarters of an inch long.
• Color – Tan to greyish brown.
• Body – Oval shaped abdomen with fine hairs.
• Head – Flat with oversized sickle-shaped mandibles featuring needle-like teeth.

What is the life cycle of an antlion?

The larval stage of antlions can last one to three years, Brown said. When they pupate, they dig further down into the soil and form a cocoon. They later emerge as adults, which only live about a month. That’s long enough to mate and for females to lay eggs in sandy locations.

How do traps work?

Pit-building larvae dig traps by burrowing backward in a circle and flicking sand to the side, Brown said. They spiral downward until the sides form a steep, funnel-shaped pit. Pits can be three-quarters of an inch to 2 inches in circumference. Once an antlion completes a pit, it settles underneath the sand and waits.

Any insect that crosses the pit’s edge risks the sand giving way and tumbling down the steep side. If the insect is lucky enough to avoid immediate capture, the antlion flicks sand toward it. This action either knocks the prey back down or causes a landslide that drags it down toward the antlion’s waiting jaws.

Once the prey is within reach, Brown said the antlion pulls it under the sand. The antlion then injects its prey with a paralyzing toxin and digestive enzymes. The enzymes break down the prey’s internal organs and tissue, liquifying them. The antlion then consumes this “bug Slurpee” before flicking the bug’s carcass out of the pit, Brown said.