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FOURTH OF JULY
FIRE(FLY)WORKS

All across South Carolina during the past few weeks, little white booths have sprung up along highways and on edges of shopping mall parking lots. Not to be confused with open-air produce stands that offer such heavenly delights as sweet corn, fresh peaches, and vine-ripened tomatoes, the entrepreneurs of whom we speak are out to capitalize on the citizenry's unquenchable drive to make one heckuva lot of noise on the Fourth of July. We speak, of course, of roadside stores inhabited by fireworks peddlers, a species commonly found across South Carolina--but outlawed just over the border in the Tarheel State and in many other locales across the land. Here at Hilton Pond Center we are truly patriotic and invariably commemorate our country's annual Independence Day, but we never buy fireWORKS, preferring instead to sit out by Hilton Pond to watch fireFLIES instead.

All text & photos © Hilton Pond Center

Yes, tiny lightningbugs are far more subtle with their bioluminescent display than roman candles and other man-made pyrotechnics, and they're most certainly easier on our ears. Classified in the aptly named Lampyridae (Lightningbug or Firefly Family), they are neither flies nor bugs, but beetles. Unlike most beetles, their pigmented elytra (forewings)--which protect the transparent hindwings used for flight--are soft and flexible. The pronotum, an extension of the thoracic exoskeleton, extends forward and hides the top of the head, which is only visible from beneath (top photo). As a result, a ventral view of lightningbugs always makes them look to us like some sort of half-inch-tall, six-legged, bug-eyed, helmet-wearing space aliens.

Adult fireflies of many smaller species do not make light, but apparently their larval stages--called "glow-worms--always do. In fact, even lightningbug eggs are bioluminescent! In several species "lightable" females are wingless and resemble the larvae. Ligthingbugs that do make light create it in an amazing way. As the lightningbug or larva allows oxygen to enter its abdomen, luciferin--in the presence of the enzyme luciferinase--oxidizes immediately and gives off a short-lived yellowish glow. (Some fireflies have been reported to provide light with hints of blue or green or even pink.) The firefly's display is the result of a cold chemical reaction in which nearly 100% of the involved compounds are converted into light. By comparison, when electrical energy passes through a incandescent bulb filament, only 10% comes off as light, the rest being wasted as heat. Incidentally, the bioluminescent chemicals used by fireflies are appropriately named for Lucifer, or "bringer of light," an old Roman epithet for the morning star.

There are 23 known genera and about 200 species of fireflies in North America, the most common being Photinus spp. and Photuris spp. More than 1,900 total species occur around the world. Oddly, in the continental U.S. fireflies are almost never seen west of Kansas. In the summer of 1964 when we were fortunate to represent South Carolina at the National Youth Science Camp in the West Virginia, we were enchanted each evening by thousands of blinking fireflies on a grassy green at the center of camp. Delegates from the western states, however, literally went bonkers over the display, for many of them had never seen these lightningbugs that we Easterners often take for granted.

All text & photos © Hilton Pond Center

So what's the function of a firefly's fire? If you've ever accidentally squished one in your hand while trying to get a jarful, you probably noticed lightningbugs have a strong odor. This probably means they taste bad, so perhaps the light is a pre-predation warning for potential bug-eaters not to eat lightningbugs. In addition, however, entomologists have found that different species of lightningbugs blink at different rates, which implies the flashes are a ways of communicating with other fireflies--especially potential mates. (One scientist was able to identify 18 different species in the field just by observing their flash patterns.) In some lightningbug species males practice synchronous flashing, a strategy that may attract females when they are relatively scarce. As the solitary female draws near the synchronously blinking gaggle of males--a sort of super-stimulus--the fastest male out of the chute gets to mate.

Firefly larvae are carnivorous, dining on dead insects and small snails in leaf litter; some enthusiasts raise them in captivity on chopped earthworms or moist dog food. Adults prey upon living insects and sometimes other fireflies. In North America, some female Photuris lightningbugs sit on vegetation and blink a signal so similar to that of Photinus females that Photinus males sometimes attempt to mate with them. The result of this phenomenal masquerade is that the Photinus male ends up being fodder for the female Photuris. If these hapless Photinus males could talk, we bet they'd say "Phooey!"

Here at Hilton Pond Center, our fireflies start getting active in shadier places just after sunset. As the sky begins to darken, they move into more open areas, and by the time it's completely dark their activity essentially ceases. (We suspect their nocturnal flashing would continue later on moonlit nights, but we haven't had a chance to test this new hypothesis.) We find the best flights to be on slightly cooler evenings after a daytime rain. Try as we might, we haven't been able to find any glow-worms in our leaf litter, but we have seen larvae and flightless females at other locales.

One thing we did learn this week is that fireflies are very nearly impossible to photograph lit-up AND on the wing. We spent an hour or more each evening with our digital camera mounted firmly on a tripod, using various combinations of lenses, shutter speeds, and apertures while trying to catch the essence of a flitting firefly. This technique may work with a camcorder, but it seems to be all but impossible with a standard camera. You'd have to be incredibly lucky to take a still photo at precisely the time a flying lightningbug flashes in front of your lens, so that limits you to using trial-and-error time exposures. Leave the shutter open too long and the ambient light washes out the flash of the firefly; shut it too soon and the insect's delicate spark fails to register. Nonetheless, we did eventually get one photo (below) that more or less depicts our inner vision of the soft, ethereal, yellow glow of a lightningbug as it does its winged dance in summer woods. The image may just look like a scratch on the page, but to us it symbolizes both the magic of Fourth of July and the fantastic fire(fly)works display available for free every summer at Hilton Pond Center.

All text & photos © Hilton Pond Center