Meet the Ghosts

The Blue Ghost of the mountains and it’s relatives are odd, tiny fireflies that produce a steady light rather than flashing like more familiar fireflies. They belong to the genus Phausis, and there are 10 species known to science, but are certainly more that have not yet been formally described. Two of these known species occur in North Carolina. The females are “larviform,” meaning they are wingless and closely resemble the tiny, pale, predaceous larvae. The females have tiny light organs in their abdomens (the numbers vary from species to species), and when they are ready to mate, they crawl to the entrance of their burrow and emit a steady, blue-green light. The males of some species don’t have light organs and therefore don’t glow; these “dark” males fly low over the forest floor looking for their females.

The Blue Ghost (Phausis reticulata) is gaining fame as one of these species that does glow; the black, ¼ inch males in this species fly about two feet over the forest floor, emitting an earie, bluish light (it’s actually green but looks blue at a distance due to an optical illusion) as they slowly cruise around looking for females with their enormous eyes.

Piedmont Ghost firefly, male. Photo by Matt Bertone.
Piedmont Ghost male, ventral view. Photo by Matt Bertone.

Females have 2-12 light spots, and are about the size of a grain of rice. When a male spots a female, he plummets to the forest floor and rapidly approaches her. If there are large numbers of males flying, many may simultaneously go to her, and a ball of fighting males is the result! Once the female mates she retreats to her burrow, where she’ll lay eggs and guard them until she dies. Once the eggs hatch, the larvae feed on other small invertebrates that live in the soil.

Piedmont Ghost female. Photo by Matt Bertone.

Blue Ghosts in the southern Appalachians have two peaks of adult activity. While the timing varies with elevation, the first peak is usually in May and the second, smaller peak, about 4-6 weeks later. Each peak lasts about 2 weeks.  Blue Ghosts prefer rich, relatively undisturbed woodlands. The other described species that occurs in North Carolina, Phausis inaccensa, is one of the “dark male” species and does not light up.

In the Piedmont, and perhaps further east, another, undescribed species of glowing Ghosts is being found. These exhibit much the same behavior as the Blue Ghost, but the males are considerably dimmer (their light organs are smaller than the Blue Ghost), and all the females we’ve found so far have only two light spots. These “Piedmont” Ghosts seem to prefer drier habitats than those preferred by Blue Ghosts, consisting of mixed hardwood and pine forests. Their peak of activity occurs the last half of April and the first half of May. The nightly activity during their flight will begin about 45 minutes after sunset, and they may only fly for 20 or 30 minutes. It needs to be absolutely dark to see them, and activity will be limited if the temperatures are much below 60 degrees F.

We have much to learn about these fireflies, including how widespread they are, and whether or not there is adult activity later in the summer. This is where you come in! Visit our Participate page to learn more about how to make observations for the Carolina Ghost Hunt.