Photo Courtesy of Cory Franklin
Orfelia fultoni is the only bioluminescent species of flies in North America, usually found in the Appalachian Mountains. They are also referred to as "foxfire flies," or as "dismalites" due to their large population in the Dismals Canyon. They were discovered in the 1940s by B.B. Fulton and classified by Elizabeth Gault Fisher.
They emit the brightest blue (λmax = 460nm) compared to other bioluminescent insects. They are distantly related to the Australian-New Zealand Arachnocampa, a genus of bioluminescent fungus gnats with similar behaviors. However, the O. fultoni bioluminescent system differs from Arachnocampa. They both share a luciferin-luciferase reaction but O. Fultoni's bioluminescence is activated by the presence of dithiothreitol (DTT), not adenosine triphosphate (ATP).
O. fultoni has four stages in its life cycle: egg (7-9 days), larval (6-9 months), pupa (approximately 2 weeks), and adult. The larval stage is the longest and where it is most recognizable. During this stage, it emits its bioluminescent glow and it is the only time it feeds. The larva has a translucent brownish appearance when not glowing and measures 10 to 20 mm long. It can be spotted during their spring peak of late April and the fall peak at the end of September, or less frequently throughout the rest of the year. Once an adult, it only lives long enough to mate and reproduce.
They are able to spin sticky, gauzy webs, similar to orb spiders, and use their head and tail lanterns to attract and trap other insects there. Once trapped, their prey is exposed to the deposits of mucus and oxalic acid decorating the web and they are paralyzed. Prey includes other small flying insects such as midges, mayflies, and caddisflies.
They reside in stream banks, among crevices and cavities protected by rocks, plants, and surrounding natural materials. Dark, still areas are preferred in order for their glow to show and to preserve their web against natural conditions. This environment protects them against changing temperatures, humidity, and drought, and it also aids in their survival on a large scale. As climate change disrupts and displaces, O. fultoni's habitat remains stable and sustainable.
Entomologist Gary R. Mullen states:
One thing you can say about them is they’re survivalists. They have survived there for these tens of thousands of years, so our climate change now is not so significant that it will affect them. They may be about the last group of organisms in Alabama, really in the Southeast, that would be affected by the climate change we’re talking about. They have all the ingredients they need to survive for many millennia. (Cromwell 2025)
Photo courtesy of Eric C. Maxwell
References:
Amaral DT, Johnson CH, Viviana VR. 2021. RNA-Seq analysis of the blue light-emitting Orfelia fultoni (Disptera: Keroplatidae) suggest photoecological adaptations at the molecular level. Comparative Biochemistry and Physiology Part D: Genomics and Proteomics. 39:100840. https://doi.org/10.1016/j.cbd.2021.100840
Cromwell S. 2025. 'Starlight' survivalists. Southern Science. https://southern-science.com/2025/02/10/starlight-survivalists/.
Franklin C. 2024. Photo 451907817. https://www.inaturalist.org/photos/451907817.
Fulton BB. 1941. A Luminous Fly Larva with Spider Traits (Diptera, Mycetophilidae). Annals of the Entomological Society of America. 34(2):289-302. https://doi.org/10.1093/aesa/34.2.289
Gigandet M. 2023. Meet the Glowing 'Worms' of the American South. Atlas Obscura. https://www.atlasobscura.com/articles/glow-worms-of-the-american-south-tennessee.
Henion LA. 2025. These elusive insects glow electric blue—and are only found in Appalachia. National Geographic. https://www.nationalgeographic.com/animals/article/appalachian-glowworms-blue-bioluminescence.
Marchiori CH. 2024. Bioluminescent fungus gnat (Diptera: Keroplatidae). In: Definitions. Qeios. https://doi.org/10.32388/GPS8R7
Maxwell EC. 2018. Photo 23433532. https://www.inaturalist.org/photos/23433532.
nannaria. 2014. The poisonous web of a bioluminescent fly. Millipede Lab. https://millipedes.ento.vt.edu/the-poisonous-web-of-a-bioluminescent-fly/.
Viviana VR, Hastings JW, Wilson T. 2002. Two Bioluminescent Diptera: The North American Orfelia fultoni and the Australian Arachnocampa flava. Similar Niche, Different Bioluminescence Systems. Photochem Photobiol. 75(1):22. https://doi.org/10.1562/0031-8655(2002)075%3C0022:TBDTNA%3E2.0.CO;2
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