Doodle Bugs Love Droughts

Forrest M. Mims III

During the ongoing drought, the doodle bugs around our place on the Geronimo Creek in Central Texas are experiencing a population explosion.

Doodle bugs, also known as ant lions (Myrmeleon sp.), are the larval insects that construct funnels in dry soil to trap ants and other insects that slide down to their waiting jaws.

Doodle bugs begin life as an egg laid in soil by a flying female. The eggs hatches into a tiny larvae, which digs a small funnel in dry soil to trap its prey. Fire ants are favorite snacks.

As the doodle bug grows, it increases the size of its trap. The largest ones on our place are just over two inches across.

When a potential meal begins sliding down the side of a doodle bug’s trap, loose grains of soil precede it. When these arrive at the bottom of the trap, the doodle bugs throws soil toward the prey to speed its descent.

When the prey arrives at the bottom of the trap, the doodle bug immediately grabs it with its powerful jaws and drags it into the soil. After the prey is consumed, the doodle bug pulls what remains to the surface and throws it out of the trap with a swing of its powerful neck.

Eventually the doodle bug surrounds itself within a silk-lined capsule of soil. It then emerges as a flying adult that looks much like a damsel fly.

There are so many doodle bug traps around our place that I decided to find out how much time a doodle bug requires to excavate its trap.

I set up a special camera that takes 100 photographs at any predetermined interval. I assumed that an hour or so might be necessary and set the camera accordingly.

I was surprised to learn that a doodle bug can fully excavate a 5-cm (2-in) wide funnel trap in only about 15 minutes! A camera isn’t even necessary to watch the process.

When the elapsed time photos were strung together to speed up the trap excavation to 10 seconds, details of the undertaking became more obvious. The doodle bug begins excavation by walking backwards just under the soil, usually starting in a clockwise direction. Every half body length or so, it throws out a jet of tiny pebbles and soil with a rapid sweep of its head and jaws. Even pebbles larger than the doodle bug are tossed out.

As it spirals deeper, the doodle bug may suddenly cut across to the opposite side of its emerging funnel and begin digging in a counter-clockwise direction. Maybe this is to switch the muscles that are used to throw out those jets of soil.

The web has some excellent doodle bug sites. Search on doodle bugs here or visit this site for starters.

Forrest M. Mims III and his science are featured online at www.forrestmims.org and www.sunandsky.org.