News and ResourcesTigers On Delmarva - March 12, 2017
In sandy dunes and shady forests across Delmarva, a tiger stalks its prey. His sleek body is poised to strike at its hapless quarry; his large eyes are focused, laser-like on his victim. His six spindly legs flex robotically and his massive mandibles masticate menacingly as he leaps into action, darting across the soil at blistering speed and seizing his prey in powerful jaws. Finished with his meal, the tiger opens his wings and fumblingly flies away, searching for his next target.
This powerful life-and-death struggle occurs right under our toes, when we’re at the beach or taking a hike through the woods. Here on the Eastern Shore, our tigers are insects no bigger than a thumbnail, easily overlooked, but often more ferocious than the real thing. The state of Maryland boasts twenty-three species of these fearsome hunters, known colloquially as tiger beetles. Tiger beetles are a large group of ground-dwelling insects that earn their name through a reputation for aggressive predatory behavior. Since most species have biting mandibles as long as their heads, that reputation is well deserved.
These beetles will eat just about anything they get their mandibles on; ants, spiders, grasshoppers, even other tiger beetles. While they certainly look menacing, their impressive jaws are more for holding prey in place and “chewing” than tearing and biting (most of the real work is done by digestive enzymes). The genuine predatory power of the tiger beetle originates from its sharp eyes and incredible speed. The tiger beetle possesses a highly developed visual system which it uses to lock on and then ambush prey items with some of the fastest footwork in the insect world. An Australian species, Cicindela hudsoni currently holds the record for world’s fastest running insect at a whopping 5.6 mph. Now this may not sound very fast, but keep in mind the size of these creatures; at 5.6 mph he is travelling 120 body lengths every second! For reference, cheetahs only cover about 16 body lengths per second and world class sprinter Usain Bolt tops out at a measly 6. In fact, tiger beetles run so quickly that that they effectively blind themselves; their eyes cannot process the information fast enough to form an image (It’s sort of like spinning in a circle as fast as you can, everything just becomes a blur). In order to make up for this temporary blindness, tiger beetles use a unique staccato hunting strategy where they speed towards their prey, stop and reorient, then continue hunting. Of course the question arises, how do they stop themselves from smashing into obstacles at top speed? The answer is simple and elegant: switch to touch when you can’t see. A pair of flexible antennae held out in front of the beetle bounce into any possible hurdles, and the tiger beetle adjusts accordingly.
The unusual larva of the tiger beetle is just as voracious as the adult. After the females lay their eggs in mid-July through August, the larvae hatch and dig themselves a long burrow. Like something out of a science fiction movie, the young insect lies in wait for unsuspecting prey and then shoots like lightning out of its burrow to grab its victim. The creatures even look a little bit like the giant worms from “Tremors”, with a long, segmented body and a thick head with powerful mandibles. One hometown subspecies of tiger beetle larvae, Habroscelimorpha dorsalis media, exhibits an unusual behavior rarely seen in the animal kingdom: when threatened by predators it leaps into the air, grabs its tail, and rolls like a wheel to safety, powered by the wind! Those of you who don’t believe me, or who want to see this incredible exhibition for yourself, keep your eyes peeled for circular holes on Worcester County’s sandy beaches. If you’re lucky, you may be able to witness this unusual display.
Many species of tiger beetle love the habitat that the Chesapeake and Coastal Bays provide. The sandy soil and open coastal marsh is perfect for their predatory style (less things to smash into when you’re blindly sprinting), and for their larvae to make burrows. If you’re walking through the loblolly pine forests and you spot a flash of brilliant metallic green, you’ve likely just seen a Six-Spotted Tiger Beetle, Cicindella sexguttata. While many people mistake this vibrant beetle for the invasive emerald ash borer, this insect is a common and beneficial predator here in Maryland. The Six-Spotted Tiger Beetle loves eating ants and caterpillars, and will gorge itself on your garden pests.
Canoe or kayak through the sandy shored of Janes Island State Park in late June through early September and you may catch a glimpse of the threatened Eastern Beach Tiger Beetle, Habroscelimorpha dorsalis dorsalis. Head to Assateague Island and the Coastal Bays around the same time, and you may see two highly rare species, the Eastern Pine Barrens Tiger Beetle (Cicindela abdominalis), and the Ghost Tiger Beetle (Ellipsoptera lepida). Eroding cliff shorelines of the Chesapeake Bay in Cecil, Kent, and Calvert counties are some of the only places in the entire world where the endangered puritan tiger beetle, Ellipsoptera puritana, is found.
Regardless of where you fall on the controversy surrounding the protection of these beetles, seeing one is a truly rare opportunity. If you spot any of these wonderful insects, watch for their unusual hunting behavior and see if you can keep up.
Simons is a volunteer with the Maryland Coastal Bays Program.
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