The bright language of firefly love
Many of us have fond childhood memories of seeing fireflies flashing in our yards or fields. Who could resist the urge to catch and watch them flashing in a jar? Their flashing is actually a language of love.
There are over 2,000 species of fireflies worldwide and more than 270 species in North America. Pennsylvania is home to 16 species, and the Pennsylvania firefly (Photuris pensylvanica) is Pennsylvania’s state insect. Another common firefly name is lightning bug, but they are not true bugs. Fireflies are not true flies but beetles that thrive in marshy, humid areas.
These reminders of carefree summers only live as adults for a month before the females mate, lay eggs, and die. Three weeks later, the eggs hatch, and the larvae live in leaf litter and soil for the next one to two years. If you look closely, you may see the glowing eggs and larvae. This glow and the flashing of adults are due to a chemical reaction in their bodies called bioluminescence. What we take for granted as a sign that school is out for the summer is a unique mating ritual in adult fireflies.
The nocturnal flashing we enjoy watching in the adult stage is a very intricate dance. The male blinks in a pattern specific to his species as he flies around in an open area. The female usually sits nearby in tall grass or brush. If she likes his dance and is willing to mate, she answers with her specific blink pattern until the male finds her.
There can be a twist to this mating ritual. Some females intentionally learn the blink pattern of the males of other species, luring them in to feed upon him. These females absorb the toxins from the ingested males and pass this into their eggs as a chemical defense system.
The peak season for firefly watching in Western Pennsylvania is June to July. With persistence, you can learn to recognize the blink patterns of different firefly species in your backyard.
The males of the synchronous firefly (Plotinus carolinus) have evolved to flash simultaneously, increasing their chances of mating. This beautiful display was once thought only to be seen in the Great Smoky Mountains of Tennessee. In 2012, this same species was found in the Allegheny National Forest. An entire festival has been created to celebrate this magical show in late June near Kellettville, Pa. Find information at pafireflyevents.org.
Sadly, firefly populations have been on the decline worldwide. Researchers suggest this is due to the use of pesticides, loss of habitat, and light pollution. We can support firefly populations by reducing our use of pesticides and decreasing unnecessary lighting in our yards during the early summer months.
With some simple changes, our yards can create safe habitats for all stages of firefly life. Allowing some taller grassy areas and forest litter piles gives the females ample areas to sit and watch for the males. Creating a pond adds humidity, which the fireflies appreciate. Also, leaving soil and leaf litter undisturbed at the end of the season will protect any eggs and larvae.
Penn State Extension has additional information about summer garden visitors at extension.psu.edu/summer-garden-visitors and at the Pennsylvania Department of Conservation and Natural Resources at www.dcnr.pa.gov/GoodNatured/Pages/Article.aspx?post=132.
If you have questions about fireflies, call the Penn State Extension Master Gardeners of Butler County at the Garden Hotline at 724-287-4761, ext. 7, or email the Master Gardeners at butlermg@psu.edu.
Jennifer Hundertmark is a Penn State Extension Master Gardener of Butler County.
