Fireflies: Romance, Deception and Intrigue Coming to a Backyard Near You

Image of Photuris sp. firefly.
Photuris sp. firefly by day, deadly deceiver at night?

Here in the northern hemisphere, there are a variety of start dates for the beginning of summer. For parents of young children, summer may start the day after school ends. For others, Memorial Day and the associated long weekend is the start to summer. And of course there’s the vernal equinox, the longest day of the year, on or around June 21, for those that favor official timelines.

For yet others of us, summer begins with a trigger from nature: The first day above 90°F, or the day the tomatoes are planted, or when June bugs first appear on the back screendoor.

One of my favorite signs that summer is really here is the mid- to late-June appearance of fireflies. Few things are as magical as the displays of these flying bugs with their delicately flashing lanterns.

Fireflies could be said to mirror a good summertime movie. While they are appealing for their magical, romantic lighted displays, they are also chemical wonders that are capable of romantic trickery and deception.

And then there is death by firefly (unintentional though it is). Fireflies, if ingested by the wrong creature, can cause a truly horrible ending.

For those unfamiliar, here are some basic firefly facts, courtesy of National Geographic.

Fireflies can be found flying over lawns, meadows and at the edges of streams and woods, beginning at dusk during the summer months. Their lighted displays differ amongst the various firefly species (approximately 170 species in the U.S. and upwards of 2,000 species worldwide) and a beetle specialist or trained observer can differentiate various species based on their signaling patterns, that is the number and duration of flashes, as well as the time between signals. For example, the male Photinus pyralis flashes a single beam during upward flight, making a “J” shape in the air. The Photinus female responds with a single flash.

On the other hand the male Photinus consumilis signals with a serious of rapid flashes, evoking a two-flash response from the female of that species.

Not only are different lantern flash patterns characteristic of particular species, different species emit differently colored signals. Photinus sp. have yellow flashes of light, while Photuris sp. flash green and Pyractomena sp. have an amber light.

While their flashing lights may appear delicate, death by firefly is far from pretty. Cornell University in Ithaca, NY published a 1999 press release about firefly toxicosis that should be read by bearded dragon  lizard owners and zookeepers everywhere.

As in any good romance novel or movie, there is the possibility of deception. Yes, the lovely lighted displays are designed  to attract a mate. The male flying above flashes and watches for a response from a female below.

Unfortunately, danger sometimes lurks for the romeo with the lantern.

The firefly Photuris sp. sometimes mimics the flashed response of Photinus females, to attract the male Photinus. Her intent? Greed and self-preservation, not romance. She is after a chemical compound that Photinus fireflies possess, used in defense against predators such as birds, spiders and other insects. The scheming Photuris sp. females lure the Photinus males down, then kill and eat them to gain this chemical.

Lucibufagins are the protective chemicals found in the “blood” of Photinus sp. fireflies. After eating the Photinus male, the female Photuris has detectable amounts of lucibufagins in her system, useful in reducing her threat from predation.

The fireflies here, however, seem to be thriving, so mating is hopefully winning out over deception (the movie has a happy ending). We’d love to hear the reports from your neck of the woods. Where are you enjoying fireflies this summer? What colors and signaling patterns have you seen?

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Kari Kenefick

Kari has been a science writer/editor for Promega since 1996. Prior to that she enjoyed working in veterinary microbiology/immunology, and has an M.S. in Bacteriology, U of WI-Madison. Favorite topics include infectious disease, inflammation, aging, exercise, nutrition and personality traits. When not writing, she enjoys training her dogs in agility and obedience. About the practice of writing, as we say for cell-based assays, "add-mix-measure".

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