Fireflies
Creature Feature
The emergence of fireflies each summer helps us transport back in time and reconnect with our childhood sense of wonder around these magical creatures…
Photo by Mike Lewinski
A Lit Life Cycle
Some people call them “fireflies”, others call them “lightning bugs”. They neither flies nor bugs; they are beetles.
Common Eastern Firefly (Photinus pyralis) by Jody Green
They get these nicknames because they light-up/flash as adults at night. It is a way that males attract females and that females then communicate back to males.
Male Common Eastern Firefly (Photinus pyralis) in flight by Terry Priest
Though variable among different species, in general the male flies around and flashes in an attempt to attract a female(s). Females typically are positioned on vegetation and will flash back at him if she is interested; that is the only way the male(s) can find the females.
Spring Tree-Top Flasher (Pyractomena borealis) larva by Nick Tobler
In most species the female lays eggs on, or just below the surface of, the ground shortly after mating. The eggs hatch, the larvae grow and live within the soil. They then hibernate over the winter in the soil, or some under tree bark, and emerge the following spring/summer as adults.
Sneaky Elf (Pyropyga decipiens) firefly by Douglas Hooper
On average adults live about two months, though this varies considerably among species. Their main purpose as an adult is to reproduce. Some species are so specialized towards this that they don’t even have any mouthparts as adults.
Winter Firefly (Photinus corruscus) mating by Juvia Heuchert
Quite Diverse
There are over 150 different species in North America, including more than 25 species found in New England. There are three main groups: Photinus, Pyractomena, and Photuris.
Ignited Firefly (Photinus ignitus) by Christian Back
Photinus make up about 2/3rds of the species in New England; they are relatively small (~1/2 inch long) and produce a yellowish-green flash.
Spring Tree-Top Flasher (Pyractomena borealis) fireflies mating by Will Kuhn
Pyractomena are similar in size as Photinus. They are distinguishable based on a raised ridge that runs down the middle of their head shield (called a “pronotum”). Their flashes are amber-colored…often likened to a ember from a campfire.
Cape Breton Firefly (Photuris fairchildi) by Bex Goreham
Photuris are notably larger (up to ~1 in long), have long thin legs. And often have a light stripe that runs diagonally down their wing covers (called “elytra”). They have greener and brighter flashes than Photinus fireflies.
Time-lapse photo of fireflies by Bernd Thaller
You can identify individual species based on the combination of the color of their flashes and the pattern of their flashes. In particular the number of flashes, duration of flashes, and the amount of time between flashes. Some by the shape their successive flashes make.
Photo by Oliver Clark
Bioluminescence
While used for mating purposes, it is believed that bioluminescence by fireflies evolved as a warning to predators of their toxicity. This is analogous to the bright orange color of Monarch Butterflies, some newt species, etc. which warn of their toxicity. When attacked by a potential predator, many fireflies exude drops of blood that contain toxic chemicals as a deterrent.
Little Gray Firefly (Photinus marginellus) by Betsy Lambert
The bioluminescence of fireflies is incredibly energy efficient. It is nearly 100% efficient, which means that almost no energy is lost in generating the light. Incandescent lightbulbs, in contrast, are only 10% efficient; 90% of the energy produced by them is lost as heat.
Underside of a Common Eastern Firefly by Anna Hess
Fireflies emit light (“bioluminesce”) from a chemical reaction that occurs in a specialized organ in their lower abdomen.
Snappy Single Sync (Photuris frontalis) firefly by Skitterbug
Femme fatale
Photuris fireflies are predatory as adults. Sometimes this includes eating other fireflies!
Pennsylvania Firefly (Photuris pennsylvanica) by Jacy Lucier
Specifically, female Photuris fireflies often mimic the response flashes made by female Photinus fireflies. Male Photinus fireflies get lured in, and then when they get close enough, the female Photuris firefly captures and eats them.
Cape Breton Firefly (Photuris fairchildi) by Bex Goreham
This serves two purposes: one is as food for the Photuris female, the other is as a source of protective toxins. Photuris fireflies are unable to produce their own toxins, but are able to incorporate toxins from the consumed Photinus fireflies to make up for this.
Don’t use herbicides or pesticides.
Reduce light pollution around your home: Learn more here
Let sections of your lawn grow tall into mid-summer.
Plant native wildflowers and shrubs.
Contribute your observations to Firefly Atlas