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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Destination Volcán del Toro, Costa Rica: Two-spotted tiger beetle, 'Pseudoxycheila tarsalis'


Clever defenses help protect the bold two-spotted tiger beetle from its enemies on the rainforest floor.


This week we leave the Eastern Hemisphere and head to Central America to visit fascinating denizens of cloud forests and rainforests. Our first stop is the caldera of an extinct volcano in Bajos del Toro. Along a winding descent to the floor of the caldera, we were greeted by a six-legged flash of cobalt blue with two large white spots on its wing covers dashing along the trail. The amazing montane two-spotted tiger beetle is a voracious predator, hunting insects, spiders, and other soft bodied prey. Like the North American six-spotted green tiger beetle featured in a previous episode, this fast-moving marauder employs saber-like jaws to capture and impale its victims, which are then sliced and diced before disappearing into its gullet. Larvae of this tiger beetle are ground dwellers that also prey on small animals on the forest floor. Unlike many cryptic and camouflaged insects, including walking sticks and leaf insects we met in recent episodes, this bold predator makes no attempt to hide from its would-be predators. It employs several clever defenses to escape capture by the beaks and jaws of birds, lizards, and other hungry animals. It’s first super power is rapid speed. Attempting to film this beetle was a real challenge. While escaping the nosy lens of a camera, one beetle covered more than 12 inches in about 3 seconds - roughly 0.2 miles per hour. Now figure this sprinter is only about half an inch long. If it were as large as, let’s say Usain Bolt, it would be moving something like 31 miles per hour, just nudging out Bolt’s world record for the hundred-meter dash.

Observe the gorgeous two-spotted tiger beetle as it searches for food at cruising speed. Now watch what happens when a bug geek surprises it. The first clip is at full speed, the second slowed by 70%.

If speed fails, the two-spotted tiger has another trick up its sleeve, or should we say up its rear-end. Upon attack by a predator, glands in the abdomen of the beetle release a veritable witch’s brew of noxious compounds including benzencarbothioic acid, hydroxy-benzoic acid methyl ester, tridecane, isoheptadecanol, octadecane and tetramet. What predator enjoys a mouthful of that? Bold humans who sampled this concoction reported a “burning sensation” on their tongues. Yikes! The final super power of this beetle lies in the two enigmatic white spots on is elytra, that is, its outer wing covers. To learn the secret of this striking color pattern, join us next week at Bug of the Week.


Bug of the Week thanks Orlando for inspiring this episode and Dr. Paula Shrewsbury for providing the image of the two-spotted tiger beetle. The article “Chemical Defenses in the Tiger Beetle PSEUDOXYCHEILA TARSALIS Bates (Carabidae: Cicindelinae)” by Tom D. Schultz and J. Puchalski was consulted in preparation for this episode.