Six-spotted tiger beetles (Cicindela sexguttata) are zipping around forest trails in Ohio. During our weekly BYGL Zoom Inservice this past Tuesday, Curtis Young (OSU Extension, Van Wert County) reported seeing adults out and about in northwest Ohio and I’ve been spotting beetles in the southwest part of the state.
Both the common and scientific names for six-spotted tiger beetles are descriptive. "Cicindela" in Latin means "glowworm" and refers to flashes of sunlight bouncing off the beetle's highly reflective surfaces.
The specific epithet "sexguttata" joins the Latin for six (as in sextuplets) with the Latin guttata which means spotted or speckled. The spots on the six-spotted tiger beetle are arranged along the trailing edge of the hardened front wings (elytra), with three spots per side.
However, some variants of the tiger beetle sport eight spots. If you look closely at the images below, you’ll spot two spots in the middle elytra.
The overall color of the shiny six-spotted tiger beetles varies from deep emerald green to blue. I've never photographed a blue form and once believed it was a trick of the light with reflective shimmering shades fluctuating from deep emerald green to slightly bluish-green depending on the angle of the light. However, there are enough images posted on reputable websites including bugguide.net that show blue-colored six-spotted tiger beetles to convince me there it's a true color form.
Research has shown that the tiger’s curious affinity for hanging out on forest trails is related to thermoregulation. Insects are “cold-blooded” (ectotherms) meaning their internal body temperature is regulated by their external environment. Six-spotted tigers are forest insects where sunlight is patchy. The beetles seek the sunny spots on the bare soil of forest trails to bask in the warming rays much like lizards sunning themselves.
Tiger beetles (family Carabidae (Ground Beetles); subfamily Cicindelinae (Tiger Beetles)) behave much like their larger feline namesake. The tiny tigers don’t lounge around waiting for a passing meat meal. They use their long, powerful legs to hunt down their arthropod prey which can be just about anything; even some things that can bite back like spiders.
They use their powerful, forward-thrusting, sickle-shaped mandibles to grab, dispatch, and disarticulate their hapless victims. A word of caution: these carnivores can also use their impressive mandibles to deliver a painful bite to the hand of the overly curious.
Six-spotted tiger beetles have excellent eyesight. Their bulging black eyes (the better to see you with, my dear!) makes them look like they're wearing goggles. I'm always amazed at how fast they can detect me before I detect them. If you spot one on a forest trail, approach slowly and watch what it does. Usually, it will spin around to face you.
If it gets too nervous, it may just use its long legs to scoot away a short distance; they are very fast runners. They are also fast, agile flyers. If things get too intense for the beetle, it will fly away. Actually, it's more like zip-away; it's like they just disappear. The tigers are difficult to photograph often appearing as blurry green streaks!
Six-spotted tiger beetle larvae are also predators. However, instead of actively hunting their prey, they conceal themselves in vertical burrows in the soil to await luckless victims. When a meat item walks past, the tiger larva springs forth like a jack-in-the-box to grab dinner with their powerful mandibles.
The bottom line is that six-spotted tiger beetles are highly effective and important beneficial predators throughout their life cycle. So, keep your eyes peeled for and hands away from these tiny tigers prowling our woodland trails ... and don't kill them!
Kaulbars, M.M. and R. Freitag, 1993. Geographical variation, classification, reconstructed phylogeny, and geographical history of the Cicindela sexguttata group (Coleoptera: Cicindelidae). The Canadian Entomologist, 125(2), pp.267-316.
Schultz, T.D., 1998. The utilization of patchy thermal microhabitats by the ectothermic insect predator, Cicindela sexguttata. Ecological Entomology, 23(4), pp.444-450.