Firefly

Fireflies are the beetles of the family Lampyridae, a group also known by the common names lightning bugs and glow-worms. More than 2,000 species have been described worldwide, and researchers suspect that 3,000 more remain to be discovered or named. All known firefly species are bioluminescent as larvae.

Light is produced when oxygen combines with ATP and the chemical luciferin in the presence of the enzyme luciferase. The reaction proceeds in two general steps: first luciferin is adenylated, then the AMP ester reacts with oxygen to reach an excited state. In the second step of the reaction the adenylated intermediate is oxygenated to produce excited-state oxyluciferin, AMP and carbon dioxide. The decomposition of a dioxetanone intermediate results in light emission from excited-state oxyluciferin through the CIEEL mechanism. Firefly luciferase is a bifunctional enzyme that can act as both a luciferase and a long-chain fatty acyl-CoA synthetase.

Unlike a light bulb, which produces much heat alongside light, a firefly's light is cold light with little energy lost as heat. The firefly photic organ uses almost 100 percent of its energy to produce a cold light. With Photinus pyralis luciferase the emission maximum is about 565 nm, yellow-green at pH 7.6, and the light turns red under acidic conditions. The color of firefly bioluminescence, ranging from green to orange-yellow, is set by the structure of the enzyme luciferase. The quantum yield was first estimated at 0.88 and later revised to 0.41. By gel filtration the enzyme was crystallized, yielding 30 mg of protein from about 6,000 firefly specimens.

Researchers learned that nitric oxide gas plays a critical role in the control of firefly flashes. In isolation from their peers, Photinus carolinus fireflies show no intrinsic rhythm in when they flash.

The enzyme that underlies firefly light, luciferase, is understood to have originated from a fatty acyl-CoA synthetase through gene duplication in insects, and beetle bioluminescence is thought to have emerged from ancestral fatty acyl-CoA synthetase enzymes. The common ancestor of fireflies arose approximately 100 million years ago and is thought to have evolved green-light luciferase in the mid-Cretaceous as an aposematic warning against nocturnal predators. A single adult male preserved in Burmese amber dating back 100 million years shows an obvious photophore structure on its abdomen.

The firefly life cycle unfolds across one to two years, and the greater part of that span is passed in the larval stage, which can last up to two years and is likely the most vulnerable period of the insect's existence. During this prolonged phase the larvae feed on snails, worms and smaller insects in leaf litter. Because those prey organisms are themselves sensitive to disturbance, threats to snails, slugs and earthworms may cascade to firefly populations.

The adult stage is brief by comparison, lasting only three to four weeks, and many adults do not feed at all.

Disturbed fireflies release lucibufagin, a bitter defensive chemical, and birds and mice learn that the insects taste bad. Because warning coloration cannot be seen at night, yellow, green and sometimes blue flashes advertise these lucibufagins. Larvae use their glows as warning displays.

Fireflies also exhibit reflex bleeding, emitting droplets of blood from the elytra and pronotum when disturbed. This behavior is generally regarded as defensive and can be potentially considerable in volume.

Photuris females entrap male Photinus fireflies by faking the Photinus female flash signal, luring them with a delay that imitates the female response. By feeding on Photinus males they acquire lucibufagins they cannot produce themselves. Females that have eaten Photinus males or lucibufagin are rejected by Phidippus jumping spiders.

Photinus carolinus flashes a sequence of five to eight distinct flashes followed by an eight-second pause of darkness before the cycle repeats. In their natural habitat these fireflies produce periodic bursts of flashes with a temperature-dependent period generally around 12 s.

When sufficiently many Photinus carolinus fireflies gather into a mating swarm they align their flashes on the same tempo.

The Elkmont area of Great Smoky Mountains National Park shelters a large population of synchronous fireflies. Since 1993 recorded peak dates at the park have ranged from the third week of May to the third week of June.

The Western Firefly Project has confirmed new firefly populations in 28 of Utah's 29 counties and in six other western states.

The IUCN Firefly Specialist Group is compiling data on extent of occurrence, area of occupancy and population size in preparation for Red List assessments. It aims to compile existing knowledge for 2000 lampyrid species worldwide on their geographic range and population size.

Initial IUCN Red List assessments covering 132 firefly species from the United States and Canada were published in 2021, about 79 percent of described species in the region. At least 18 species, or 14 percent, were categorized as threatened, while more than half of the assessed species are data deficient.

Fish and Wildlife Service issued a positive 90-day finding for the loopy five firefly, Photuris forresti, under the Endangered Species Act.

Among the pressures acting on fireflies, habitat loss was perceived as the most serious threat both globally and within nearly all regions, with artificial light at night second and pesticide use third.

The Malaysian case illustrates what habitat conversion can do to a single species. Breeding congregations of Pteroptyx tener declined after riverbank mangroves were converted to agriculture, aquaculture and urban use.

Evidence for these declines remains uneven. Long-term monitoring studies in the United States and Canada are sparse, but a growing body of anecdotal reports indicates that many fireflies are declining.

From 1960 until about 1995 a chemical company harvested about three million North American fireflies a year to extract luciferase and luciferin. Firefly tourism collectively attracts more than 200,000 visitors per year and carries considerable economic benefits.

Through roughly 16,500 submissions Firefly Watch participants tracked fireflies at nearly 7,000 locations across the United States. Mass Audubon passed the Firefly Watch project to the Xerces Society, a science-based nonprofit that protects wildlife through invertebrate conservation. The Western Firefly Project began in 2014 as the Utah Firefly Citizen Science Project before expanding to other western states in 2019 and beyond.

The Selangor Declaration of 2010 urges governments to protect and restore firefly habitats and to support funding for firefly research.

• 1929
  Oldest Utah firefly specimen collected
  The oldest firefly specimen in Utah was collected in 1929 and is housed at the Natural History Museum of Utah.^{10Western Firefly Project: A Community Science Initiative · Natural History Museum of Utah ↗}
• 1956
  Firefly luciferase crystallized
  Firefly luciferase from the lanterns of Photinus pyralis was crystallized.^{6Firefly luciferase: an adenylate-forming enzyme for multicatalytic functions · PubMed Central (peer-reviewed review) ↗}
• 1965
  Femmes fatales described
  James E. Lloyd's study of aggressive mimicry in Photuris fireflies appeared.^{16Firefly 'femmes fatales' acquire defensive steroids (lucibufagins) from their firefly prey · PNAS (via PubMed Central) ↗}
• 1968
  Buck and Buck analyze synchronous flashing
  John and Elisabeth Buck's analysis of rhythmic synchronous flashing in Southeast Asian fireflies appeared in Science.^{8Emergent periodicity in the collective synchronous flashing of fireflies · eLife ↗}
• 2014
  Western Firefly Project begins
  The Western Firefly Project began as the Utah Firefly Citizen Science Project.^{10Western Firefly Project: A Community Science Initiative · Natural History Museum of Utah ↗}
• 2018
  IUCN Firefly Specialist Group established
  The group was established to assess the conservation status and extinction risks facing fireflies worldwide.^{14A Global Perspective on Firefly Extinction Threats · BioScience, Oxford University Press ↗}
• 2019
  Western Firefly Project expands
  The project expanded to other western states in 2019 and beyond.^{10Western Firefly Project: A Community Science Initiative · Natural History Museum of Utah ↗}
• 2024
  Bethany Beach firefly proposed for listing
  Responding to a petition from the Xerces Society and the Center for Biological Diversity, the Fish and Wildlife Service proposed listing the Bethany Beach firefly.^{13Loopy Five Firefly to be Considered for Endangered Species Protection · The Xerces Society for Invertebrate Conservation ↗}