Fireflies

Nights in your backyard at this time of year are filled with spectacular light displays created by lightning bugs, otherwise known as fireflies.  There are over 170 different species in the U.S., and fireflies can be found in every state except Hawaii, and on every continent except Antarctica.  The flashes are a form of communication, mainly for trying to attract a mate.

Not all fireflies in the U.S. are ‘flashers’.  Some species are active only during the day and do not emit any light; several species are known as glowworms and emit a steady, glowing light.  Here in the Midwest and farther east, most species are ‘flashers’.  Flashing is a form of communication used in seeking and finding a mate.  The light is a byproduct from a bio-chemical reaction of oxygen with the enzyme luciferan plus ATP and manganese.  Different species will emit different colors of light from green to yellow to orange.  Colors can also be influenced by what time of day it is and how well they will show up against the background colors of the habitat.  Firefly enzymes have been widely studied by medical research facilities where doctors have been able to inject the enzymes into a test specimen and  duplicate the light emission to provide imaging of internal cell structures.  This procedure, known as bioluminescence imaging, is at the forefront of emerging technologies for studies of viral infection.

Fireflies are part of the beetle family and as in all species in this family, they undergo complete metamorphosis including four stages: egg, larva, pupa, and adult.  Fireflies lay eggs in late summer in rotting logs, moist soil or deep mulch.  Larvae hatch in three to four weeks, and they are voracious predators of soft bodied invertebrates including snails, slugs, spiders, and earthworms.  Larvae live from one to two years, overwintering underground or deep in rotting wood.  They molt often during this stage of eating and growing.  Larvae pupate in late spring either in an underground burrow or in some species, by attachment to a tree branch where they hang upside-down.  In two to several weeks, depending on the species, a biochemical transformation will take place changing the larva into an adult.  After adults emerge, their only function is to reproduce.  Adults generally do not eat, but may sip nectar or maple sap as a secondary source of moisture.   They live only a few weeks finding a mate and laying eggs  before they die.

Fireflies can be found in a wide variety of habitats including rivers, valleys, ponds, fields, marshes, forests, cities and urban areas.  There has been very little scientific study of firefly population characteristics, and we are just starting to accumulate this data.  Therefore, little is known as to whether they are declining, but there is anecdotal data to suggest that there were many more fireflies thirty to fifty years ago.  It is known that 3/4 of all species are active only at night.  Species in our area can be affected by habitat loss, herbicide use, and artificial night light which can obscure firefly communication and adversely affect breeding success rates.

It is fun and entertaining to be out on a quiet evening and enjoy the light displays being put on by these small insects.  You can help keep their populations strong in several ways.  Retention of leaf litter and logs, especially rotting wood, in forested or other areas will provide spaces for egg laying and larvae to live.  Consider reducing outdoor lighting at night including garage and walkway lights and buildings with all night lighting.  The use of motion detectors on timed circuits so lights are only on for a limited amount of time will greatly cut down on the amount of light present at night.  We hope you get out to see these wonderful gems, but remember if you are out looking for fireflies that flashlights, cell phones and camera flash units are all forms of artificial light that are best avoided to enhance your outdoor viewing experience.