Our Window on Nature

. . . exploring the world around us

Summer’s Flashing Fireflies

Filed under: Bugs — Lowell Christie -- July 24, 2015 @ 3:22 pm

firefliesPinpoints of light danced the minuet across our darkened lawn, a visual counterpoint to the dozens of chirping crickets and the distant drum roll of thunder. Such are the memories of hot, muggy Midwestern summer evenings.

Miles away and decades later, we paused in our drive along the Blue Ridge Parkway. The air was heavy with the scent of white and red and pink roses, so we close the windows  of our motorhome (proving that even amid such beauty, allergies take precedence over aromas).

As night draws near, the roses and the grasses are clothed with flashing lights, this time of a slightly different flashing pattern and a somewhat different color.

The fireflies we caught in Mason jars during childhood and those seen in the Blue Ridge Mountains were merely two of many species of fireflies. These tiny insects, biological if not intellectual marvels, produce light ten times more efficiently than man can hope for. Much light; little heat — not bad for a bug.

Flashing in fireflies plays a pivotal role in the process of attracting mates. Male fireflies generate most of the flashing since they do it while on the wing, but it’s the females who stir them into action. They flash a come-hither signal from near or on the ground (making them easier for children bearing Mason jars to catch). When a male notices her flash, he replies with his own signal, and they begin the series of signals and responses that ultimately result in mating.

After breeding, the male, ever the bachelor, returns to the pursuit of other flashy females. Ordinarily, female fireflies stop flashing once they’re bred, but at least one species continues to flash for a reason we’ll discuss in a moment.

Once in a while, too often to be mere coincidence, all fireflies within range of eyesight begin signaling in unison much as crickets sing in unison, as though all are led by the same conductor. The length and duration of each flash, the length of interval between flashes and between each complete signal pattern, the number of flashes contained in a signal pattern, and, to some extent, the color of the light produced, are species specific written in the genes of individual fireflies so that they are recognized only by others of its kind. Species recognition is further aided by each species’ preference for time of day and choice of habitat for flashing

Now for the species whose females flash after mating. With an altogether different purpose in mind, she now ignores the flashing of her own species and begins mimicking the flashing patterns of other species. Males who come to breed are captured and eaten. Or to put it nicely, she recycles them into eggs of her own species. For as we already know, female mosquitoes and fleas need a blood meal … why not female flashers.

Blood and gore aside, the female concentrates on egg laying. Over the next couple of days she deposits eggs singly, either on or just under the soil. After about four weeks gestation, the larva hatch and begin eating and eating. They are definitely carnivorous, with a passion for worms and snails. Upon the arrival of autumn, cool weather and shorter days trigger the instinct of the larva to burrow underground and overwinter.

Hearty appetites once again drive firefly larva above ground in early spring. They eat all the way to summer. At long last their appetites wane (or possibly they have eaten all the edibles in the area) and they burrow underground again, this time to pupate. About two-and-a-half weeks later, adult fireflies emerge, ready to dance and entertain as they continue their cycle of life and light.


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