Antlion (family Myrmeleontidae)

Antlions are a strange group of insects, in the family Myrmeleontidae. Technically, the term antlion applies to the larvae of these bugs, and there is no commonly used term for the adults in English. I can see why, as the adults are pretty boring run-of-the-mill insects. But that’s okay, because the larvae are super interesting. And they’re called antlions. Which is a pretty sweet name. Another name for antlion larvae is ‘doodlebugs’, which describes the marks the insects leave in the sand while wandering around.

Antlions, like many insects, go through distinct stages in their lives. The first and most interesting is the larval stage. Antlion larvae usually live in sandy areas, and dig themselves into the ground for shelter. One interesting thing about antlions is that larvae do not have an anus. Instead, the larva stores the waste it generates and later excretes it at the end of the pupal stage. The pupal stage of the antlion is characterized by the spinning of a silk and sand cocoon, which is usually buried in the sand. After a month the adult antlion emerges from the cocoon. Adults can be considerably larger than the larvae, and in fact have the greatest size disparity between adult and larvae of any metamorphosing insect.

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An adult antlion

The most fascinating part about these little guys is the way the larvae hunt. Antlions eat ants and other small bugs, and they capture them by building sand traps. Not quite the same as those found in a round of golf, but just as nasty. Nastier, in fact. The antlion wanders around searching for the perfect place to build its trap (hence the ‘doodles’ in the sand), and when it does its starts an excavation process. Using its abdomen, the insect shovels sand to the edge of the pit. There it uses one of its legs to place the sand on its head, and then flicks its head backwards, clearing the dirt from the pit. The antlion repeats this procedure until it has dug out the pit, usually about 2 cm deep. Then the larva crawls into the pit backwards, and sits buried at the bottom with its jaws open.

So far it seems like a pretty amazing feat for a little bug, right? And the idea is fairly simple: an ant walks into the pit and gets snapped up in those waiting jaws. But it’s even better than that. After all, what’s to stop that poor ant form just climbing out of the pit? Well, the antlion thought of that. So what it does is dig the trap just until the sand is at the critical angle of repose, a state where the slightest disturbance causes a cascade of falling sand. When a ill-fated ant steps into the pit, it disturbs the sand and slides into the waiting antlion. If the ant tries to scramble out of the trap, the antlion simply throws sand at it until the ant falls to the bottom. It doesn’t even matter if the antlion’s aim is good or not; the tossed sand is enough to disturb the sides of the pit and cause the ant to come tumbling down into the larva’s jaws.

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The carefully dug trap of an antlion larva

Clearly somebody should make a movie about giant antlions living in the desert, trapping unwary humans who wander too close. Attack of the Killer Antlions! That sounds a lot more exciting than it probably would be. After all, as much as I wish they were, antlions are not giant crosses between ants and lions. Though that would make a great (but terrible) movie. Maybe I’ll send the script to someone at Hollywood. Or maybe not. Probably not.

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