The FIREFLY FOREST
 
 

   

    This website contains both ESTABLISHED FACTS and MY PERSONAL THEORIES (marked *) about Phausis reticulata, the “Blue Ghost” fireflies found in undisturbed forests in some Appalachian localities.  They are very unusual because the males fly with their lights on without blinking, and they normally all fly about four to eight inches above the ground.  In favorable years it is possible to see tens or even hundreds of thousands of them all flying at the same time, making a virtual “carpet of light” in the darkness of the forest.

   

    Although they are fairly widespread, there are only a few known* areas where there are as many of them as there are here in THE FIREFLY FOREST.


    The combination of undisturbed mulch and deep, rich soil here apparently supports a great abundance of whatever organisms the firefly larvae feed on, resulting in huge numbers of adults which emerge during favorable years.*


    They emerge here in mid-April, and there will usually be large numbers of them during most of May. However, their numbers vary from year to year so there is no way to predict how many there will be.  Their emergence is probably related to ground temperature and other factors such as ground moisture and daylight length.* The life span of an individual male is about two weeks.*  Most of their life cycle (which I think is two or more years*) is spent underground in the larval and pupal stages.


    There are two distinct sizes (5-6 mm and 7-9mm) of both males and females and both sizes are reported to be morphologically identical.  (See PHOTOS)  This fact, I believe, was  documented some 70 years ago, but at present I cannot reference the documentation.  Males resemble regular “lightning bugs” in miniature, and females look like tiny yellow grub worms with legs.  FEMALES ARE WINGLESS AND CANNOT FLY.  

   

    Males fly about 4 to 8 inches above the ground, emitting a CONTINUOUS green glow which lasts a minute or more, and they move at a rate of about 1 foot per second*.  Males begin flying at total darkness (about 9PM), and cease all activity by midnight.


    The males seem to space themselves more or less equidistantly apart from each other horizontally when flying.* This is especially noticeable when there are great numbers of them, on the order of one per two or three square feet of terrain.  In 1975, the first year that I saw them, there were literally millions of them, flying at a distance of perhaps 6 to 8 inches apart.


    They have been described as “visual popcorn” when they start flying each night. 


    Females probably burrow into the ground each night, as they are soft-bodied and would desiccate if exposed.* Males probably spend their non-flying time in the leaf mulch.*

Females are rarely seen, as they are usually hidden in the leaf mulch during “flying time.”  They have 2 to 8 light spots which glow continuously.  (See PHOTOS)  I have seen only 5 or 6 females with all 8 light spots glowing since I first began observing them.  Males are attracted to the females by the PATTERN of two or more light spots.*  Also, there may be a slight difference in the colors of male and female lights, which could possibly help the males identify females.*


    However, it is the female PHEROMONES which alert the males that the females have emerged from the ground each evening, and is therefore the signal for the males to start flying.*  Females will mate several times during their lifetimes.*


    The fireflies are much more active during misty, foggy nights, following afternoon or early evening light to moderate rainfall.  Such nights occur, by definition, during low atmospheric pressure conditions, when there are no air currents or updrafts to disperse the female pheromones.*


    There are indications that the males do not fly very far from the areas where they emerged, except near the end of their season when there are only few of them remaining.*  If this is in fact the case, it would almost certainly be because pheromones mark their “home” areas. 

The male fireflies will not fly in wind or when air temperature is below about 55 degrees F.  Very few of them will fly in moonlight, but they will fly in the deep shade of the evergreens.


    Violent late-afternoon/evening thunderstorms, or periods of prolonged heavy rain, will kill off most of the males, prematurely ending their season.  The larger-sized males are more likely to survive these rain events than the smaller-sized ones.*

 

    On a very dark night, if a male flies within about 2 - 3 feet of you, you can see his “spotlight” –-a circle of pale blue-green light (about 8 inches diameter) moving along the ground below and in front of the firefly.  You can’t see the firefly light itself, because you’re seeing the firefly from above.   The spot of light on the ground tells the firefly (A) that he is flying at the proper altitude and (B)  (possibly) that he is above leaf mulch.  Bright moonlight washes out the ground light and overpowers their vision, making it more difficult for them to navigate and to see females on the ground.*  Occasionally during the evening most of the males will turn off their lights and stop flying for short periods of time.

   

    I THINK THAT THE PRIMARY FUNCTION OF THE MALE LANTERN IS TO MAINTAIN A CONSTANT ALTITUDE AND TO NAVIGATE THROUGH THE UNDERBRUSH.*


    They may appear to be all flying toward you but they are actually flying in a “back and forth” pattern, and you cannot see their light when they’re flying away from you.


    As far as I know, the only Phausis predator is a small spider which makes a web close to the ground.  I don’t know whether this predator is specific to Phausis.  The firefly light spot continues to glow for a while, even after the firefly is dead.  So, if you see an immobile light spot, you have to look closely, to determine whether it’s a male in a spider web or a female on the ground.


    So far it has not been possible to get a real-time video of the males in flight.  I would greatly appreciate hearing from anyone who has experience with extremely low-light cinematography.


    In June 2007 I signed a Conservation Easement on this property with UPSTATE FOREVER.  I feel that this is the most effective way to protect and conserve the Firefly Forest habitat, in perpetuity.


    Don Lewis

    PO box 345

    Cleveland, SC 29635

    lewisdon@bellsouth.net

 

                              Photograph by Wayne Wheeler