Ant lion holes are small, funnel-shaped pits dug into dry sand or loose soil by the larvae of antlions, insects in the family Myrmeleontidae. Each pit is a carefully engineered trap. At the bottom, buried just beneath the surface, a larva waits with oversized jaws ready to snatch any small insect that stumbles over the edge. These pits are common under eaves, porches, rock overhangs, and anywhere else dry, fine sand stays sheltered from rain.
How the Pits Are Built
An antlion larva digs its pit by moving backward in spiraling loops, using its flat head like a shovel to flick sand grains up and out of the hole. The result is a cone-shaped depression that slopes to a single point at the bottom. Construction can take hours, and the larva adjusts pit size based on the sand available and how recently it has eaten.
The physics behind the pit are surprisingly precise. The walls slope at what engineers call the “angle of repose,” the steepest angle a pile of loose particles can hold before collapsing. In fine sand, this angle averages about 45.8 degrees. In coarser sand, it drops to around 41 to 42 degrees. Researchers at the University of California, Irvine found that antlion pits match the angle of repose almost exactly for whatever sand the larva builds in. This means the walls are always on the verge of collapse, which is the whole point.
Sand grain size matters. Finer particles produce steeper, more treacherous walls because tiny grains stick together slightly more than coarse ones. There is a lower limit, though. Particles smaller than about 0.1 millimeters start behaving like powder, becoming airborne or clumping, which makes pit construction difficult. This is why you typically find antlion pits in dry, medium-fine sand rather than in dust or gravel.
How the Trap Works
Once the pit is finished, the larva buries itself at the bottom with only its open jaws exposed. It can wait days or even weeks for a meal. When an ant or other small insect steps onto the rim, the sand gives way under its feet. The steep, unstable walls do most of the work, and the prey slides toward the center like someone trying to climb a crumbling hill.
If the insect manages to get traction and starts climbing back out, the antlion has a backup strategy. It rapidly flicks sand upward with its head, pelting the struggling prey. These sand volleys serve two purposes: they knock the insect off balance, and they trigger small landslides along the pit wall that drag it back down. The combination of unstable slopes and targeted bombardment makes escape extremely difficult for small insects.
What Happens After Capture
Once the prey tumbles within reach, the larva grabs it with large, curved, hollow jaws that work like a pair of sickles. It pulls the insect beneath the sand almost instantly. The larva then injects two things through those jaws: a paralyzing venom that subdues the prey and digestive enzymes that liquefy the insect’s internal organs and tissues. The antlion essentially drinks its meal, sucking the dissolved contents back through the same hollow jaws. When it’s finished, it flicks the dried husk out of the pit and repairs any damage to the walls.
This style of feeding, digesting prey outside the body and consuming only liquid, means the larva has no need for a conventional gut opening. In fact, antlion larvae don’t produce solid waste during their entire larval life. Everything they consume is absorbed.
Where You’ll Find Them
Antlion pits cluster in spots that stay dry and sheltered. The underside of roof overhangs, the sandy ground beneath porches, the bases of large rocks, cave entrances, and the protected sides of sand dunes are all common locations. Rain destroys the pits by compacting the sand and ruining the delicate slope angles, so antlions strongly favor areas with natural overhead cover.
You’ll rarely see just one pit. Larvae often congregate in the same favorable patch of sand, creating fields of small craters that can number in the dozens. Each pit belongs to a single larva, and pit size roughly corresponds to the larva’s age and body size. A newly hatched larva might dig a pit just a centimeter or two across, while a mature one can build a funnel several centimeters wide and deep.
The Larval Stage Lasts Years
What surprises most people is how long antlions spend as pit-dwelling larvae. The larval period lasts one to three years, depending on species, food availability, and climate. During this entire time, the larva lives underground, maintaining and occasionally relocating its pit. If prey becomes scarce, the larva may abandon a pit and dig a new one in a more promising spot.
When the larva has grown enough, it stops feeding and spins a small, round cocoon in the sand using silk mixed with sand grains. Metamorphosis takes about three weeks inside this cocoon. After roughly four weeks total underground, the adult antlion emerges at the surface and looks nothing like the creature that built the pit.
The Adult Looks Like a Damselfly
Adult antlions resemble damselflies at first glance, with long, slender bodies, two pairs of delicate mesh-like wings, and large eyes. The key difference is their antennae, which are longer and end in small clubs. Adults can reach 45 millimeters in body length with a wingspan of about 65 millimeters. Most species are brown or mottled gray.
They are weak, clumsy fliers, mostly active at night and commonly drawn to porch lights. Adults feed on nectar, pollen, and occasionally other small insects. After spending years as a larva, the adult stage is remarkably brief: about four weeks, just long enough to mate and lay eggs in sandy soil where the next generation will begin digging pits of their own.