A popular residential design of the 1950s featured homes like mine with large overhangs on the roofs. These overhangs do a marvelous job of deflecting rainwater away from the foundation. A side benefit is the creation of a veritable dessert just beneath the overhang. Some of you will recall a desert scene from George Lucas’s Return of the Jedi were a terrifying multi-toothed creature called a Sarlacc inhabited a pit on Tatooine dining on hapless Jedi Knights. Each year miniature versions of the Sarlaccian pits appear in the dusty desert beneath my eves as dozens of craters about the size of half dollars pockmark the ground. One of my favorite summer pastimes is to watch ants, beetles, and other small ground dwelling arthropods stumble into the craters and tumble down the slope. At the base of this cone of death lies a ferocious predator – the antlion. The antlion larva, affectionately known as a doodlebug, constructs its funnel-shaped trap by backing into sandy soil and carefully flicking soil particles with its mouthparts until a symmetrical pit forms.
Small ground-dwelling arthropods like ants fall into the pit and tumble to the bottom. At the base of the pit just beneath the sand, the antlion awaits its prey. Sensing that someone has dropped in for dinner, the antlion clamps the ill-fated victim in a lethal embrace with powerful jaws. The victim is often dragged entirely beneath the sand as the antlion enjoys its feast. The antlion’s jaws bear a groove used to channel blood from the living victim to the belly of the beast. After consuming the liquid portion of the prey, the antlion tosses the carcass from the pit with a snap of its head. Occasionally a large or lucky potential victim will evade the first strike of the antlion and attempt a desperate scramble for freedom up the slope. To foil the escape, the antlion flicks sand from the base of the cone towards its prey. The displacement of sand creates a Lilliputian avalanche carrying the prey down slope into the grasp of the antlion. Adult antlions are rarely seen, but often mistaken for a damselfly or dragonfly. Feeding habits of these beautiful creatures are largely unknown other than that they consume soft-bodied insects and pollen. They are often attracted to outdoor lights at night. These delicate insects lay eggs in sandy soil where eggs hatch into subterranean monsters. Upon completing their development, antlions spin silken cocoons in the soil where the transformation from larva to pupa to adult takes place. So, while hiking in the desert, if you come across a deep conical pit, stay well back from the edge lest you tumble in. You never really know what awaits at the bottom.
References for this Bug of the Week include “Effects of slope and particle size on ant locomotion: Implications for choice of substrate by antlions” by Jason Botz, Catherine Louden, Bradley Barger, Jeffrey Olafsen, and Don Steeples and “Immature Insects” by Frederick Stehr. The inspiration for this Bug of the Week came from Adam Gruner who is always ready for an antlion adventure.