Here’s a bug that’s widely recognized in its larval form and sinks into obscurity as an adult, at least as far as the public’s concerned. If you’ve ever seen the adult form you probably had no idea what it was.
It’s the antlion.
In fact, we suspect that more than a few of you are now thinking “I thought the antlion WAS an adult insect.”
Nope. It’s the larval form of a rather large flying insect in the order Neuroptera, family Myrmeleontidae.
(An interesting aside – Neuroptera is the most primitive insect order that undergoes complete metamorphosis – that is, four life stages including egg, larva, pupa and adult forms. You can read more about insect development and other entomology basics in this EDIS document.)
The adults – which don’t really have a common name, aside from “adult antlions” – have long, thin bodies, prominent antennae and four long, narrow wings that are transparent with delicate veining.
The larvae are about a half-inch long with bodies roughly the size and shape of an apple seed, short legs and no wings. Their most prominent feature is a fearsome-looking pair of oversized jaws that project forward from the head, a bit like a pair of old-time ice tongs. And those jaws are not just for show.
Antlion larvae are ambush predators. Some species lie in wait under debris and seize small insects passing by. But the species most people are familiar with have a more ingenious way to obtain their meals.
The larva digs a pit – a cone-shaped depression roughly two or three inches in diameter – in loose sand, by flinging up tiny portions of the material with its oversized head.
Then the antlion waits at the bottom of the pit, almost completely buried except its jaws. When an ant wanders by and crosses the edge of the depression, grains of sand start flowing downhill, carrying the ant along. If the ant tries to scurry back up and out, it’s likely that the sand will be too loose to offer secure footing, and the ant will inexorably slide down to the bottom. When it reaches the waiting antlion, there’s a quick flurry of movement, some flying sand, and then stillness as the antlion consumes its prey.
Generations of Southern children have amused themselves by guiding or dropping ants into antlion pits to watch the fireworks. It’s also common for youngsters to patiently blow away enough sand to expose the antlion, or just scoop up the entire pit and the surrounding sand and sift through it looking for the insect.
Florida is home to 22 antlion species, more than any other U.S. state, including four that are only found in the Keys.
Around the house, the best place to find them is any sandy outdoor area that’s shielded from rain and is almost always dry. The pits are easy to spot, and no other creature makes a similar structure.
In areas where antlions are common, you may also see tiny ditch-like trails running through the sand. These are depressions created by antlion larvae seeking good places to excavate. It’s said that these trails gave rise to the antlion’s well-known nickname, the doodlebug, because the trails resemble doodles – simple, abstract drawings.
By the way, if you’re into fun, family-friendly horror movies, the 1990 film Tremors features a monster that’s loosely based on the antlion larva, though it includes one feature that doesn’t exist in nature. (We won’t spoil the surprise.)
Here’s a UF/IFAS Featured Creatures document on one species found in Florida that lives in tree holes(!) as a larva and gives rise to an especially colorful adult.