Galloping tiger beetles roar on our beaches

Some of our southern beaches are home to tiny predators that race at top speed across the sand in pursuit of ants, fleas, flies, And small crustaceans.

These are southeastern beach tiger beetles (Cicindela dorsalis media).

Tiger beetles are a large group of active, fast-moving insect predators, and southeastern beach tiger beetles are no exception. They may be small – only half an inch long – but they’ve got massive jaws, long legs built for running, and a mottled tan body that provides camouflage against the sand.

Adults patrol the intertidal zone on warm, sunny days and early evenings, ready to clasp any live prey they can run down.

Sometimes they also scavenge dead crabs and fish.

After mating, which occurs in mid-summer, females drop eggs one by one in small holes they dig on the beach. Each newly hatched, wormlike larva builds a vertical burrow in the sand, within which it waits for passing prey. If seawater starts trickling into the burrow, the larva plugs the open end with sand. As it grows larger, it constructs bigger burrows, some as deep as fourteen inches.

Compared to the sprinting adults, the mostly sedentary larvae seem to lead a quiet life. But sometimes they become free-wheeling creatures themselves – literally.

When threatened, larvae leap into the air, twist themselves into a circular shape, and start rolling along the sand like a living wheel, aided by the wind.

This extraordinary behavior was first reported in 2011 from Cumberland Island, Ga., by Alan Harvey, a biologist at Georgia Southern University, and then-graduate student Sarah Zukoff.

Wheel locomotion has been seen in only a few other animals, such as the wheel spider (Carparachne aureoflava), of southern Africa, and caterpillars of the mother-of-pearl moth (Pleurotya ruralis), found in Europe.

Harvey and Zuckoff suggest that in beach tiger beetles wheel locomotion may help exposed larvae flee from predators, including certain parasitic wasps.

Free-wheeling larvae can travel as far as 200 feet and at speeds up to 7 mph if the wind is strong.

But their progress is slowed or halted by rough, uneven surfaces and pieces of debris. For this reason, the beetles prefer pristine, fine-sand beaches.

Unfortunately, people do, too.

Increasing development of coastal areas, along with heavy foot and vehicular traffic on popular beaches, has contributed to major population declines in beach tiger beetles.

In some parts of their range, these fascinating insects have nearly disappeared. Let’s hope we can take steps to reverse that trend.

This story was originally published May 9, 2016 at 9:28 AM with the headline "Galloping tiger beetles roar on our beaches."