Monday, August 23, 2010

Antlions — clever predators of bug world

Conical holes in the sand trap ants and other bugs that happen to crawl by

Simply Living

(First appeared in Orlando Sentinel August 22, 2010)

"Look at all the antlions you have," Tavares resident Mike Endres said, pointing at the sandy ground surrounding our bamboo gazebo. "You must know all about antlions."

Staring at the patch of pockmarked ground where he pointed, I said I knew absolutely nothing about antlions. Until Mike and his wife, Annette, visited our nursery, I had never even heard of them.

"I'm afraid I don't know what antlions are," I admitted.

"See all these conical pits in the sand?" Mike patiently explained. "Hidden under the sand at the bottom of each pit is a little bug called an antlion. It's called that because it eats ants that walk by and fall into its trap."

Image from http://natural-japan.net/?cat=26


What a surprise. I had no idea insects had purposely created all the round holes surrounding the gazebo. I had noticed the holes — they were always there — but thought that drips of water had made them. I didn't realize they were actually the work of predatory larvae that were patiently waiting to devour their prey.

"We used to call them doodlebugs," Annette added. "Maybe you know them by that name?"

Unfortunately, I did not.

The name "doodlebug" comes from the insect's meandering trail, which leaves visible, doodlelike designs in the sand. Once the crawling larva locates a suitable spot, it creates an ant-trapping pit by "drawing" a series of concentric spirals. Each spiral is a bit deeper than the previous one until the entire construction becomes a slippery, cone-shaped hole about two inches deep and three inches across. Clueless ants that wander into these clever traps rarely escape.

When the Endreses left, I knelt down next to the pit-filled ground to look more closely at my newfound friends. Any critter that eats ants earns automatic endearment. I was determined to learn as much as I could about these helpful predators with the underground homes.

Upon close inspection, I saw activity in the holes. In each pit, an almost completely buried antlion was either repairing its trap or capturing prey. While I watched, ants wandered by, slid into the holes and suddenly vanished. Antlions are just over a half-inch long, but their strong mandibles make fast work of hapless insects that fall into their lairs.

I consider myself a keen observer of wildlife, but somehow I had managed to live 58 years without even knowing that doodlebugs existed. To make up for lost time, I began to do research.

Antlions belong to the Myrmeleontidae family — insects that progress through a complete metamorphosis. The adult form is a four-winged bug called a lacewing-antlion that looks somewhat like a dragonfly. The lacewing-antlion stays in its winged stage for only a few months — long enough to lay a series of small, white eggs linked together in a horseshoe pattern on building eaves, plant leaves and even the underside of lawn furniture.

Image from http://exotic-life-creatures.blogspot.com


The eggs hatch into larvae, which are fierce-looking creatures with spindle-shaped bodies, flat heads, large, pincerlike jaws and three pairs of short legs. They transport themselves on these stubby appendages to sheltered, soft, sandy areas where they can doodle their way to dietary delight. While lacewing-antlions don't last long, the larva stage lasts for up to three years.

At some point, instinct triggers another transformation, and ant hunting gives way to the business of building a cocoon. Using a mixture of sand and its own silk, the larva constructs a globular cocoon beneath the sand, where it remains for about a month. At the end of the month, a sexually mature lacewing-antlion emerges to begin the cycle again.

I had no idea how much was happening in the ground surrounding my gazebo.

The day after Mike and Annette Endres introduced me to these small, sit-and-wait predators, another customer brought them up. For 10 years, people have visited our nursery without a single mention of antlions. Suddenly, in two days, two customers zoned in on the ant-eating insects.

This second customer was a mom who had brought along her three children. As I was explaining to her husband the differences between clumping bamboos and running bamboos, I overheard the mother teaching her elementary-age offspring.

"Do you see those circular pits in the sand? Down in the bottom, hidden beneath the sand, is a little bug called an antlion," she explained. "It's called that because, like a lion, it hunts for food, and the food this lion likes to eat are ants."

I may have not have known about antlions two weeks ago, but thanks to two customers, I am familiar with them now. No matter how long you live somewhere, you'll never know everything about your environment. There will always be surprises. There are new creatures to discover, plants to learn about, unfamiliar areas to explore.

This time it was antlions. I wonder what it will be next time?

9 comments:

  1. Fascinating post. I have never heard of them, so after reading this I googled images. OMG, they are scary looking! Lol!

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    1. I'm glad I'm not the only one who had never heard of antlions! Scary...you betcha, especially if you're an ant on a stroll across sandy ground...

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  2. omg i have these. lol thank you never knew what they were.

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  3. we used to call them doodlebugs when I was little. you twirl a stick in a a circle, through that hole, and say, "doodlebug doodlebug come out your house is on fire." and there he would be.
    lol

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    1. hi kristina - thanks for commenting. other people have told me about the saying the same rhyme when they were kids. did you grow up in the south? i grew up in PA where i guess doodlebugs/antlions didn't live so that's a rhyme/game i only learned about recently.

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  4. Was unfamiliar with what was responsible for the holes in my flower bed , until my granddaughter noticed a leg kicking sand out of the bottom - so thank you for the clarification of my holes and the wonderful ant eating bugs in the bottom - can't wait to share with my granddaughter what I've learned - Conneaut, Ohio

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  5. Was unfamiliar with what was responsible for the holes in my flower bed , until my granddaughter noticed a leg kicking sand out of the bottom - so thank you for the clarification of my holes and the wonderful ant eating bugs in the bottom - can't wait to share with my granddaughter what I've learned - Conneaut, Ohio

    ReplyDelete