Synchronous Fireflies

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Lightning bugs, or fireflies (Order Coleoptera; Family Lampyridae) are a summertime favorite.  Arguably one of the most universally loved insects, these charismatic beetles light up the sky and carry a nostalgia of warm summer nights spent capturing the little lanterns in a jar… at least for those of us lucky enough to have bioluminescent adults flying in our yards (Because, as you've learned from Joe Bogg's post- there are diurnal fireflies that have no lantern! See article here.). The fireflies are already in full swing, and the light show is ready to impress.

 

Ohio yards are commonly visited by the species Photinus pyralis, also known as the “Big Dippers”.  These large fireflies are characterized by their yellow flash that creates a “J” shaped streak in the sky.  However, last week, I witnessed a rare phenomenon, the synchronous fireflies.

 

 

a field of big dipper photinus pyralis fireflies
Photinus pyralis "Big Dipper" Fireflies in a field.  Also some Photuris tremulans "Christmas Light" fireflies in the tree tops way in the back.

 

 

The synchronous fireflies (Photinus carolinus) are a different species from our common backyard lightning bugs, and a rare sight in Ohio (though we do have some populations of them in select habitat). I had to travel to the Great Smoky Mountains in Tennessee to witness these gems. Their name gives the impression that they flash in perfect sync.  While they can match up their blink, the synchrony really is most notable when the males all “turn off” in unison.

 

 

synchronous fireflies in tennessee

 

 

The males blink their lantern (the light organ of fireflies is called a lantern) for 6 to 8 pulses while flying, creating a train of 6 or more yellow flashes in the sky. Then they quiet all together, leaving you in darkness for about 6-9 seconds, then begin anew.  It is during these periods of darkness that the males can scan the ground for a female P. carolinus who, from their hidden spots on the forest floor, will subtly flash from their smaller and dimmer lantern, in response to the males’ dazzling displays. While our backyard fliers are common sightings around dusk, these fireflies are late blinkers! They flash in the black of night after the big dippers are done for the night. 

 

synchronous fireflies

 

 

Also present during these late hours were blue ghost fireflies (Phausis reticulata). While it's hard to play favorites with these amazing glowing creatures, I think the blue ghost are my faves.  These smaller fireflies do not blink but faintly glow continuously a dim blue.  They fly low over the forest floor and, in pictures, leave a lime green trail of light as they zig and zag scanning for the female.  Female blue ghosts are larva-form. They do not develop wings or the traditional firefly coloring.  These pale worm-like females hide in the leaf litter and glow from 4-8 spots on their bodies.  It's up to the males to spot her with their cute, large eyes!  

 

 

synchronous fireflies and blue ghost fireflies in a forest
In a forest full of synchronous yellow lights, you can see the green "Trails" of the blue ghost fireflies flying low in the understory in this photo.

 

 

There are over 75 different species of firefly/lightning bug in the Eastern/Central U.S. alone! And fireflies are found on every continent other than Antarctica. We are fortunate in the Eastern US to have so many flashing species to delight us.  But we often get the question, "where are the fireflies?" "I remember more when I was younger."  In order to keep these impressive beetles in our lives, there are some things we can do to help.

There are a number of factors that might contribute to declining numbers of these and other insects. Fireflies like humid, dark, and clean environments. Turning off lights prevents competition between our artificial light and the flashes that they need to communicate and find mates. Using lower intensity bulbs, timers, or shields to prevent glare and light pollution can be very helpful.  

Fireflies live only a few weeks as adults, but spend 1 to 2 YEARS as a larva in our soil, leaf-litter, and understory debris. Leaving leaves where possible, creating leaf mulch piles, and limiting soil disturbance can go a long way to protecting the developing larva and pupa that one day become our beloved lightning bugs.  

And of course reducing pesticide use whenever possible, especially in moist areas where fireflies might be more likely to live. This is especially true of treatments for mosquitos which would be used in moist habitats near firefly zones.

 

If you want to learn more about fireflies, I recommend the book, "Fireflies, Glow-worms, and Lightning Bugs" by expert Lynn Faust.

 

extreme firefly
A composite picture of all the synchronous firefly flashes over a 2 hour period in the Great Smoky Mountain national park.