Exploring The Last Green Valley: Insect-sized pit of doom a little wonder of natural world

A couple of months ago as I was unlocking the door to my barn, I noticed a conical-shaped hole in the sandy soil next to the door sill. It looked like an upside-down volcano about two inches in diameter.

I recognized it immediately from my youthful years spent exploring the insect world in my old neighborhood. The hole was home to a diminutive yet gruesome creature – the antlion.

The antlion is not an ant but an eater of ants and other insects. The conical-shaped hole is its cleverly-devised trap to catch prey that unwittingly ventures into its lair. In fact, those familiar with the “Star Trek” film “The Wrath of Khan” will recognize a larger-scale model of the antlion “pit of doom.”

The antlion is also known as a “doodle bug” in some parts of the United States. It gets this name from the random “doodle” designs it creates in the sandy soil as it searches for the right location to build its trap. Once the right location is found, it makes concentric spirals in the loose material, each deeper than the last, until the hole is finished.

To watch the antlion catch its prey is to witness one of the more gruesome acts in the insect world. When I was a kid, my brothers and I would sit and watch the antlion at work. It was our own private horror show, something out of a frightening science fiction movie full of deadly creatures, blood and gore.

The sides of the antlion’s pit are made of soft sand that slides away as its prey struggles on the loose material. The victim slips further downward, closer and closer to the base of the pit. The antlion hides inside the pit, concealed in the steep wall, with only its jaws protruding from the sand, wide open and waiting.

When hapless victims fall into the pit, it is all but impossible for them to climb up the loose sand. The antlion will even flick sand grains back up toward the rim, deepening the hole and causing miniature landslides, knocking its prey to the bottom. The antlion then lunges with its spiny jaws and drags the victim beneath the sand.

One time my older brother showed me what the antlion looks like by taking a single, long, white pine needle and twirling it along the bottom of the pit until the antlion grabbed hold. My brother pulled it up from the loose sand, squiggling and angry, yet holding tight to the end of the pine needle.

The antlion who occupies the “pit of doom” is actually the larva stage of a much more peaceful and benign winged insect that resembles a small dragonfly or damselfly. They are from a family of insects with the zoological classification Myrmeleontidae, the name rooted in Greek with myrmex (ant) and leon (lion). Clearly its name comes from the predatory nature of the larval form.

The antlion larva is a ferocious-looking creature, though only about a half-inch long. It has six legs, and its head has a large pair of sickle-shaped jaws, or mandibles, with several sharp, spiny projections. The jaws are hollow and after piercing their victim, antlions inject venom which digests and dissolves the body contents.

By late summer, antlion larvae have transformed from their cocoon stage into winged adults. They can be found around evening porch lights or campfires but will hide during the day, well-camouflaged on branches and leaves.

What creatures are outside your door? From the smallest insect to the largest mammal, our natural world is a place of wonder to behold every day. I hope you’ll get out to experience the last month of summer. Join us as we work to care for, enjoy, and pass on this beautiful place we call The Last Green Valley.

Bill Reid is the Chief Ranger of The Last Green Valley National Heritage Corridor and has lived in the region for more than 30 years. He can be reached at bill@tlgv.org.