Saturday, March 18, 2017

Fireflies: The flash season approaches

I have always found it a little embarrassing that, as a naturalist, I never knew the differences between the fireflies in Ohio.  After all, fireflies are one of the first animals people chase as children.  If you grew up in the Eastern United States, you certainly enjoyed fireflies.  But so few people could tell you much about these glowing critters and how to identify them.  They were simply these magical beetles flittering about on summer nights, and for most of us, that's all we needed to know.  Enjoying the spectacle is something everyone can appreciate.  BUT, if you ever wanted to know more, now you can.

Yellow-bellied Fireflies, Photinus scintillans, showing the typical firefly shape and color.  many look alike, but their flash gives clue to the species identification.
I have been waiting for years for a publication to come out describing the species and life histories of these incredibly interesting creatures.  And finally, the book has arrived.  A fascinating author and friend of the preserve, Lynn Faust, has put her years of firefly knowledge together in a long-awaited field guide.  Now the rest of us can figure out who is flashing in our own backyards and when and where are the best times to search.  The book is called "Firelies, Glow-worms, and Lightning Bugs". 

Great new firefly book available now.  See link below to purchase.
You might be surprised to find out that there is more than one species of firefly.  In fact, I learned many interesting things while spending a few days firefly chasing with Lynn, and reading her book.

Did you know??
1. Not all fireflies produce light as adults, but they can as larva.
2. Firefly flash rates, intensity and color differ between the species.
3. Firefly species are seasonal and some even flash only specific times of the night.
4. Some fireflies are cannibalistic and mimic the flash of other species to lure them in, and then eat them.
5. Many fireflies are light sensitive and city lights mimicking dawn and dusk have changed the distribution of species ranges.
6. Male fireflies flash to attract females, and sometimes they flash synchronously because they are all trying to be the first noticed.

Fireflies that flash have abdominal segments that act as "lanterns" to show light created by bioluminescence. 
Pictured is the Yellow-Bellied Firefly, Photinus scintillans.

It is extremely difficult to photograph the remarkable display of light.  This photo by John Howard captures 2 flash patterns.
There is so much to learn, and Lynn has packaged all this information into one easy to read book.  I can now pick a species in the book, read about its flash pattern, what time of night it flashes, what time of year, what habitat to look in and actually find that species in the field.  It really works!

There are some fireflies that you might find in Southern Ohio this winter and spring, even though it is not quite yet the flash season.  One species you can find from late fall through the winter is the Winter Firefly, Ellychnia corrusca.  It overwinters as an adult.  This species does not flash, but from info in Lynn's book, I learned to find them on the south side of large tree trunks on sunny winter days.   

Ellychnia corrusca, the winter firefly.
One of the first flashing fireflies in the spring should start communicating through glowing abdomens in mid April.  It is the Treetop Flasher, Pyractomena borealis.  This early season beetle flashes once every four seconds in the tops of trees before the leaves grow.  It's larva can be found pupating on large tree trunks in late winter. In late summer and fall, the larva is found on the forest floor eating snails.  Pictured below is one of these larva, whose head telescopes out to reach snails inside their shell.

Spring treetop flasher larva feeding on a Northern three-tooth snail (Triodopsis tridentata). Photo by Chris Bedel.
Once May comes, the flash season begins.  Besides the Spring treetop flashers, another firefly, this one from the cannibal genus called Photuris, begins to flash.  Fields around the preserve start to fill up with the quick flashes of the Spring 4-Flashers,  Photuris versicolor var. quadrifulgens.  These beetles appear to stutter as they flash 4 times.  By the first weeks of June, this species will disappear before other species begin flashing.

Fireflies in the genus Photuris (like these P. quadrifulgens) have long legs and large pronotums, usually with a black "anchor" mark.
By June, many more species begin to flash, some right before dark like the Little Grays,  Photinus marginellus, and some right at dark like the very common Big Dippers, Photinus pyralis.  This, in Southern Ohio, is the real flash season.  The majority of firefly species will be out in June and July.  By then, we should all be skilled at counting flashes, observing flash patterns and be expert firefly hunters thanks to Lynn's field guide.
Other species found on the preserve with the help of Lynn Faust are:

The lanternless species
Sneaky Elf, Pyropyga decipiens
Woodland Lucy, Lucidota atra

The lanterned flashing species
Synchronous Firefly, Photinus carolinus
Mr. Mac, Photinus macdermotti
Creekside Tree Blinkers, Photinus sabulosus

The carnivorous species
Slow Blues, Photuris caerulucens
Chinese Lanterns and the Flashbulbs, Photuris sp.
Heebie-Jeebies, Photuris hebes
July Comets, Photuris lucicrescens
Dot-Dash, Photuris pennsylvanica
Variable Triple Flash, Photuris versicolor

This will be the year to find more new and unusual firefly species on the preserve.  Watch for blog posts this summer about new species and some of the interesting species mentioned in the above list. 

I cannot think of another long-awaited book that all naturalists need in their libraries. To purchase this great new book on fireflies, search the title on or click on link below.

Posted by: Mark Zloba