Photinus pyralis

Geographic Range

The common eastern firefly, or North American firefly, ranges throughout the United States east of the Rocky Mountains. ("Firefly", 2001)


Larvae of the common eastern firefly most often inhabit moist places such as on the ground, under bark, and near streams. Adult fireflies can be found from late spring to early fall in meadows, woodland edges, and near streams. (Milne and Milne, 1980)

Physical Description

The common eastern firefly is, in fact, not a fly, but a type of beetle. The average adult is dark brown and 10-14 mm long. Like all insects, it has a hard exoskeleton, six jointed legs, two antennae, compound eyes, and a body divided into three parts head, thorax, and abdomen). Its head has a rounded cover outlined in yellow and accented with two orange spots. Photinus pyralis also has two pairs of wings. The first pair, the elytra, form a cover over the second pair and is dark brown with narrow yellow side margins. Only males use the second pair for flying; females usually have short wings, and do not fly. The last segment of the abdomen is the section that lights up, flashing bright yellow-green.

Common eastern firefly larvae are characterized by six legs, a pair of antennae, and a flattened segmented abdomen. Upon emerging from the egg they are generally about 1.6 mm in length. By the end of its larval stage it will have grown to about 10.3 mm. Firefly larvae are often referred to as "glow worms" because, like the adults, they emit a glow of light. ("Firefly or Lightning Bug: Photinus pyralis", 1999; Arnett, 1985; Grzimek, 1972; Milne and Milne, 1980; Tweit, 1999)

  • Sexual Dimorphism
  • sexes shaped differently
  • Range length
    10 to 14 mm
    0.39 to 0.55 in


Firefly eggs, which also emit a slight glow, hatch after four weeks into flightless larvae, the longest stage of the firefly life cycle. Larvae live one to two years and can be seen glowing on damp ground and near streams. After passing through the larval stage, the developing firefly moves into chambers in the moist soil and pupates. While pupating, it undergoes metamorphosis, emerging from the pupa as an adult. ("Firefly or Lightning Bug: Photinus pyralis", 1999; "Firefly", 2001; Milne and Milne, 1980; Pesson, 1959)


Fireflies use specific flashing signals to find a mate. Females wait on the ground for passing males to flash their signal, and then answer with their own specific signal. It is this communication that allows the male to find a female with whom he mates. ("Firefly or Lightning Bug: Photinus pyralis", 1999; "Firefly", 2001; Milne and Milne, 1980; Pesson, 1959)

Fireflies use specific flashing signals to find a mate. Females wait on the ground for passing males to flash their signal, and then answer with their own specific signal. It is this communication that allows the male to find a female with whom he mates. This dating game occurs in summer and early fall, and the female generally lays about 500 eggs on damp soil during this time of year. ("Firefly or Lightning Bug: Photinus pyralis", 1999; "Firefly", 2001; Milne and Milne, 1980; Pesson, 1959)

  • Average eggs per season


Adult Photinus pyralis live 5 to 30 days. (Grzimek, 1972; Milne and Milne, 1980)

  • Typical lifespan
    Status: wild
    5 to 30 days


Firefly larvae spend winter and early spring burrowed into the soil. In late spring, they emerge to feed. Adult fireflies use their glow to both ward off predators and attract mates. It was originally thought that the light signals of the firefly would attract predators; however, the common eastern firefly contains a steroid that is poisonous, and this deters potential predators such as birds and frogs.

The light signal benefits P. pyralis most during mating. At dusk males take flight while females wait perched on the ground or in bushes. While in flight, the male emits, on average, a 0.3 second flash every 5.5 seconds. This particular signalling sequence is specific to P. pyralis; however, it is the females's response that enables the male common eastern firefly to find a mate of the same species. The female flashes a response approximately two seconds later, a specific and crucial interval for this firefly species. Once the male recognizes the female P. pyralis, it flies down to the ground where mating takes place. ("Firefly or Lightning Bug: Photinus pyralis", 1999; "Firefly", 2001; Grzimek, 1972; Tweit, 1999)

Communication and Perception

  • Communication Channels
  • visual

Food Habits

Both adult and larval Phorinua pyralis are carnivorous. They feed on other insects (including other fireflies), earthworms, and snails. When feeding, they inject poison to immobilize and liquefy their prey. This allows the fireflies or larvae to suck up their meal. ("Firefly or Lightning Bug: Photinus pyralis", 1999)

  • Animal Foods
  • insects
  • mollusks
  • terrestrial worms


An interesting predator of Photinus pyralis is the female Photuris pyralis. This firefly mimics the signal of the female Photinus pyralis and lures male Photinus pyralis that are expecting to mate. However, when the male common eastern firefly reaches this mimicking species, he quickly becomes the female predator's meal. (Milne and Milne, 1980)

  • Known Predators
    • Photuris pyralis

Economic Importance for Humans: Positive

The chemical utilized by the common eastern firefly for bioluminescence is a complex organic compound, luciferase. Fireflies have recently been harvested by the biochemical industry for this important compound. Researchers discovered a technique to splice the gene containing luciferase into the DNA of other plants and animals. They use this in tracing the inheritance of a particular disease-resistant gene by splicing the bioluminescence gene into the disease-resistant gene in a parent plant or animal. The disease-resistant gene can then be traced in the offspring, because if it is inherited, it will glow. ("Firefly or Lightning Bug: Photinus pyralis", 1999; Tweit, 1999)

Economic Importance for Humans: Negative

There is no known negative economic importance for humans.

Conservation Status

This species does not require any special status.

Other Comments

Photinus pyralis is the most common of 1900 species of fireflies.

The firefly produces light in the presence of oxygen, magnesium, and adenosine triphosphate by using an enzyme, luciferase, to oxidize a complex organic compound, luciferin. The light produced is often referred to as "cold light" because almost all the energy is released in the form of light and very little is wasted as heat. The wavelength range of this light spans from 520-620nm, and its brightness reaches 1/40 that of a candle. This bright light is what attracts most of the common eastern firefly's popularity. ("Firefly or Lightning Bug: Photinus pyralis", 1999; "Firefly", 2001; Arnett, 1985; Grzimek, 1972; Milne and Milne, 1980)


Sara Diamond (editor), Animal Diversity Web.

Jenny McKenzie (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


eats mollusks, members of Phylum Mollusca


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


generates and uses light to communicate


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season


offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


living in residential areas on the outskirts of large cities or towns.


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


uses sight to communicate


1999. "Firefly or Lightning Bug: Photinus pyralis" (On-line). Accessed April 12, 2001 at

2001. Firefly. Pp. 134 in World Book. Chicago: World Book Incorporated.

Arnett, R. 1985. American Insects: A Handbook of the Insects of North America and Mexico. New York: Van Nostrand Reinhold Company.

Grzimek, D. 1972. Grzimek's Animal Life Encyclopedia. New York: Van Nostrand Reinhold Company.

Milne, L., M. Milne. 1980. The Audobon Society Field Guide to North American Insects and Spiders. New York: Chanticleir Press.

Pesson, P. 1959. The World of Insects. New York: McGraw-Hill Book Company.

Tweit, S. 1999. Dance of the Fireflies. Audubon, 101, Issue 4: 16,28-31.