The Ant Lion is a common insect in Florida, and indeed it is found in most of the United States. But despite its wide range and common distribution, most people have never seen the actual insect. Instead, we know it by the conspicuous cone-shaped traps that it makes, often in large groups, in suitable flat sandy areas.
Ant Lion. Actual size about 3/8 inch.
The insect family Myrmeleontidae (the Latin translates literally as “ant lion”) contains over a thousand different species around the world, ranging from large tropical versions to smaller types in temperate areas like Europe. We have about a hundred different species in North America.
In Florida, the pit traps can often be found in bare sandy areas in lawns or city parks. They are often clustered together rim to rim, looking like a miniature moonscape. The little pits are actually the equivalent of a spiderweb–they are the tool used by the Ant Lion to catch its prey. If you use a trowel to very quickly dig up the sand underneath the pit trap, and then carefully sift through it, you will find the pit’s maker. Ant Lions look like something out of science fiction (in fact, the Ant Lion was the inspiration for the alien creature that figured so prominently in the plot of the scifi movie Star Trek III: The Wrath of Khan). The Ant Lion measures up to half an inch long, with a bulbous body covered with bristles, six legs, a flat head, and two enormous sickle-shaped jaws fitted with sharp spines. As protection from predators, it has a gland in its abdomen that allows it to squirt formic acid.
What you are looking at is actually the larval stage of a flying insect, the Lacewing. The adult looks nothing like the larva–it resembles a small thin damselfly with long curved antennae. Although it can often be seen near lights at night, most people don’t recognize the connection between the Lacewing adult and the Ant Lion larva.
The Ant Lion’s life begins when a female Lacewing lays her eggs in a suitable patch of sandy soil that is sheltered from rain under a tree or rock. These hatch into tiny larvae, who space themselves out and dig their pit, using their flat heads to flip sand away. (Sometimes the larvae must crawl over the sand for some distance to find a suitable spot, and they leave a wandering trail behind them–leading to the name “Doodlebug”). The size of the finished pit varies with the size of the insect; typically they reach an inch and a half wide and an inch or so deep. At the bottom of the trap, the Ant Lion buries itself until just the tips of the jaws protrude above the sand. And waits.
It’s just a matter of time until one of Florida’s ubiquitous ants wanders in, slips on the loose sand at the sloping sides of the conical trap, and falls in (and the Ant Lion, once it senses the vibrations, will often use its flat head to toss sand on the ant to help knock it down). At the bottom of the pit, the ant is seized in the Ant Lion’s strong jaws, is pulled under the sand, and becomes lunch. After the body has been drained of its innards, the empty husk is tossed out, the Ant Lion buries itself again, and the trap is re-set. As the larva molts and grows, it makes bigger and bigger pits. As they get bigger, they are also capable of handling larger and larger prey, including small beetles or spiders.
After about two years, the Ant Lion larva will dig itself deeper into the sand and pupate, forming a little round silken cocoon. About a month later, the adult emerges and, once its wings have hardened, it flies off. The adult only lives a short time–just long enough to find a mate and lay new eggs.
Hidden History 
When I was a kid we sometimes tried to entice the ant lion out of its lair by simulating a struggling insect with a piece of straw. But they were almost never fooled. Rather strangely, I very seldom see the adult form around here.