by Timothy Loftus
AUBURN, Mass. – The doodlebug waits. It is patient. It is silent. And it is hidden under a fine layer of dry, loose, sandy soil at the bottom of a small conical pit. Soon, a wandering ant will slip down the side of the pit, where the sickle-shaped mandibles of the doodlebug will rise from the bottom to grab the ant. The doodlebug will inject paralyzing venom into its prey, followed by digestive fluids that turn the ant’s insides to liquid. Then this hungry doodlebug will slurp the juices before flicking the desiccated ant carcass out of its pit trap. Constantly hungry, the doodlebug hides again at the bottom of the pit and waits for its next meal to stumble in.
Doodlebugs are the larval stage of winged adult antlions in the myrmeleon genus. The antlion family (Myrmeleontidae) includes some 2,000 species worldwide, and roughly 100 species in North America, one of which, Myrmeleon immaculatus, is commonly found in northern New England. Doodlebugs create conical pits, which they use to catch their prey. The larva is mottled gray and brown, up to half an inch long, and has a plump body covered in tiny bristles to help anchor itself in the soil while capturing prey with its long, strong jaws.
Doodlebugs are named for the meandering trails, or “doodles,” they leave in the loose, sandy soil as they seek the perfect spot to dig their pits. When that spot is found, the doodlebug makes a circular groove outlining the top edge of the pit. Then, crawling backwards, the doodlebug uses its body as a plough and its head to flick the loose sandy soil away from the construction site. Round and round it goes, spiraling toward the center and deeper into the soil. Depending on the size of the growing larva, its pit can be up to three inches in diameter and two inches deep.
The doodlebug pit trap is an engineering marvel. The sides of the conical pit are angled so that with just a slight disturbance from an ant or other small invertebrate, part of the trap will avalanche, carrying the prey to the bottom of the pit, where the powerful jaws of the doodlebug eagerly await. If the prey tries to escape by climbing out of the trap, the doodlebug flicks sand or grit into the air to knock it back down and to further weaken the side of the pit to create another mini-avalanche for a second try at capturing its next meal.
For centuries, doodlebugs have also captured the imagination of people worldwide and have been referenced in riddles, literature, folklore and in superstitious chants. Doodlebugs and antlions have found places in the books of Mark Twain, John Steinbeck, Arthur C. Clarke, and Henry David Thoreau. Even Charlie Duke, Apollo 16 astronaut, thought lunar craters resembled doodlebug pits, and recited part of a childhood chant while on the moon: “Doodlebug, doodlebug, are you at home?”
Here on earth, doodlebugs build their pits in areas of loose, dry soil protected from rain. The pits are often under porches, along shady riverbanks, or on open woodland floors, all areas that ants like.
Doodlebugs can remain in their larval stage for several years, spending the cold winter months inactive in the soil, waiting for the warmer months to dig their pit traps again. Their growth depends on the availability of the food source, usually ants and oftentimes other small insects and invertebrates, and they can survive many months without feeding. Eventually the larva will form a ball-shaped cocoon in the soil, and about a month later, the adult version of the doodlebug, commonly called an antlion, emerges.
Adult antlions resemble dragonflies and damselflies, but have clubbed antennae. Their 2½-inch-long wings fold tent-like over their thin 1½-inch-long bodies. They are active at night, feebly flying around searching for a mate. Adult antlions feed on pollen and nectar and, depending on species, live for about 25 to 45 days. During this short time, a female will lay up to 80 eggs, singly, in loose, dry, sandy soil, starting the next generation of antlions.
[Tim Loftus is an environmental chemist and writer based in central Massachusetts. Illustration by Adelaide Murphy Tyrol.]