Invertebrates
Antlion
Myrmeleontidae · also called antlion, doodlebug, ant lion
The antlion is two completely different animals in one life. For years it is a squat, sand-buried larva with scythe jaws, sitting at the bottom of a cone-shaped pit trap and pelting sand at anything that tries to climb out. Then it emerges as a slender, dragonfly-like adult that lives only a few weeks.
Overview
Antlions are a family of about 2,000 species found in dry, sandy places on every continent except Antarctica — dune hollows, cave mouths, the base of walls, and under overhangs. The larva is a predator; the adult looks like a weak dragonfly with clubbed antennae and eats pollen, nectar, or small insects.
The pit trap
The larva digs by spiralling backwards, flicking sand with its head, to make a steep funnel 2–5 cm across in fine dry sand. It buries itself at the bottom, jaws exposed. An insect that slips over the rim slides down; if it struggles, the antlion hurls sand upward to collapse the slope and carry the prey into its jaws, where it injects paralysing venom and digestive enzymes and sucks it dry.
A body with no exit
The larva’s gut has no anal opening — it stores every scrap of waste for years and voids it just once, as a newly emerged adult.
Doodlebug
Searching for a pit site, the larva leaves winding trails in the sand like idle scribbles — the source of the American name “doodlebug” and the rhymes children use to coax one out.
Status
Antlions are Not Evaluated, generally common wherever there is sheltered dry ground, though pit-builders need undisturbed fine sand out of the rain.
Antlion: common questions
How does an antlion pit trap work?
The larva selects fine, dry, loose sand in a sheltered spot out of the rain and wind, then digs by moving backwards in a tightening spiral, using its flat head as a shovel to fling sand outward over the rim. The result is a smooth-sided cone, its slope sitting right at the sand's angle of repose — the steepest angle it can hold before slipping. The antlion buries itself at the bottom with only its jaws exposed. When an ant or other small insect wanders over the edge, the loose slope gives way and it slides toward the centre. If it starts to scramble back out, the antlion flicks volleys of sand up at it with sharp jerks of its head, which both knocks the prey down and collapses the pit wall, carrying the victim into the jaws.
What does an antlion do once it catches prey?
It seizes the insect with its long, curved, hollow jaws and pulls it under the sand. The jaws are grooved and paired with slender maxillae to form sucking tubes. The antlion injects saliva containing venom that paralyses the prey and digestive enzymes that liquefy its tissues from the inside, then sucks out the resulting fluid, often within a few minutes. The empty husk is then flicked out of the pit with a toss of the head, and the antlion repairs any damage to the funnel and settles back down to wait. A larva can survive long stretches — weeks or months — between meals if prey is scarce.
What does an adult antlion look like?
Nothing like the larva. The adult is a slender, soft-bodied insect with two pairs of long, narrow, heavily veined wings that it holds tent-like over its back at rest, and it looks very much like a damselfly or a small, weak dragonfly. The quickest way to tell an adult antlion from a damselfly is the antennae — an antlion has fairly short antennae with a distinct club or swelling at the tip, while damselflies and dragonflies have tiny bristle-like antennae. Adult antlions are mostly active at dusk and night, are weak, fluttery fliers, and are often drawn to lights. They live only a few weeks, just long enough to mate and, for the female, to lay eggs in sandy ground.
Why is the antlion called a doodlebug?
Before a larva digs its pit, and if it has to abandon a poor site, it travels just under the surface of the sand in search of a better spot, leaving a winding, looping furrow behind it. These trails look like aimless doodles drawn in the sand, which earned the larva the affectionate American name "doodlebug." In the southern United States there is a long tradition of children reciting rhymes — "Doodlebug, doodlebug, come out of your hole" — while poking a straw into a pit, in the belief it will lure the larva up; what actually happens is the antlion mistakes the disturbance for prey and grabs the straw.