Did you know that there are 29 known species of fireflies (Lampyridae) in eastern Canada and 19 of which have been found in Ontario?1 These beetles can be found in June and July in grassland, woodland and wetland habitats where they light up the night (usually around dusk) using bioluminescence (light production through a series of chemical reactions within an organism).1,2
Fireflies have a special enzyme (a protein that acts as a catalyst and causes the acceleration of a chemical reaction) called luciferase which causes a chemical reaction between oxygen, another special protein called D-luciferin, ATP (Adenosine triphosphate which is a form of chemical energy in cells) and Mg2+ (magnesium ion).3
This series of reactions causes the beautiful yellow/orange/red light that fireflies produce and each species expresses this light using unique patterns of flashes!1 Not only is the light beautiful it is also efficient and actually uses 20% less energy than walking!4
Why do fireflies glow?
Although the larval stages of many species are not documented, it is theorized that they all exhibit bioluminescence.1
In fact, it is thought that fireflies actually evolved bioluminescence as a visible display, like colour, that signals to predators that a species is unpalatable, toxic and/or dangerous, and later was adapted for use in adults .4
Mature fireflies use bioluminescence to attract mates in the darkening dusk skies or even to lure their next meal! In mating rituals males (which will usually flash when flying) and females (which will usually flash while on the ground, regardless of whether they have the ability to fly- females of some species cannot) will “speak” to each other through their carefully timed flashing patterns.4
Once a love connection is sparked the male will fly down to the female in hopes of taking their romance to the next level. In some species, charming males will actually bring nuptial gifts of prey, spermatophores (a package containing sperm and nutrients) or offer parts of his body for food (this sparks a whole new meaning of “giving yourself to someone”!) to females in order to woo them.4 
If she finds the male worthy she will mate with him; however if a female waits too long and doesn’t select a male, the quality of their gifts deteriorate (this I because males will often mate with more than one female)!4
Instead of only signaling to find mates, females of some firefly species will mimic the signaling pattern of females of a different type of firefly, thus inviting the male from that species to come over for an amorous rendez-vous or what he thinks will be a romantic night. The, when he flies to her, perhaps bringing his thoughtful gifts, she climbs on top him and EATS him.4 I can imagine the scene “Hello beautiful lady, I brought you some dinner and gifts?” “Thank you, sir :D” *CRUCH* “MUAHAHA YOU are dinner!”
As mating season progresses to late summer females will lay their eggs in the ground or under tree bark. 5
After a few weeks larvae hatch and will overwinter in either place.5 Larva can be terrestrial, semi-aquatic or aquatic and eat worms, snails or other squishy invertebrates.1 Due to the fact that they live most of their lives in the larval state in/on the ground this means that soil health is very important for them! Anything applied to the ground, such as pesticides, can have negative effects on firefly populations either directly through killing them or through killing their prey.
A flash for love that no one can see. Does she notice me?
Our fireflies are in trouble. Landscape changes causing habitat loss and light pollution (artificial lights on at night) causes firefly lovers to become lost. Fireflies adapted their lighting to be noticed in a dark environment, but what happens when we light up the night sky with artificial lights? Studies have shown that outdoor lighting, even when it is 88% less intense than street lights, reduces the frequency and occurrence of firefly flashing by a staggering 50% compared to nights without lighting (little moonlight, no artificial light)!2
The reduction in firefly flashes is likely to greatly reduce instances of mating because males and females have a harder time finding each other.2 Some studies have shown reductions in flashing up to 69%!6 In 2001, it was calculated that nearly 19% of land experienced light pollution with that percentage advancing up to 6% each year. 7
Single and ready to mingle: What can we do to help fireflies find love?
With night lighting and light pollution being one of the greatest threats to fireflies (and many other nocturnal species) the best thing we can do is reduce the intensity and frequency of artificial lighting in the environment.
Fireflies are a marvelous and almost magical species. By doing something as simple as turning off our lights when we are not using them, we can help these beauties to shine bright all summer! Learn about how to help fireflies and build firefly habitat by watching “How to Attract and Protect Fireflies” . To learn more about effects of light pollution please visit The International Dark-Sky Association website.
Written by:
Fallon Hayes, Communications and Education Specialist
Works Cited
- Luk, Stephen PL, Stephen A. Marshall, and Marc A. Branham. “The fireflies of Ontario (Coleoptera: Lampyridae).” Canadian Journal of Arthropod Identification 16 (2011): 1-105.
- Costin, Kevin J., and April M. Boulton. “A field experiment on the effect of introduced light pollution on fireflies (Coleoptera: Lampyridae) in the Piedmont Region of Maryland.” The Coleopterists Bulletin 70.1 (2016): 84-86.
- Fleiss, Aubin, and Karen S. Sarkisyan. “A brief review of bioluminescent systems (2019).” Current genetics 65.4 (2019): 877-882.
- Lewis, Sara M., and Christopher K. Cratsley. “Flash signal evolution, mate choice, and predation in fireflies.” Annu. Rev. Entomol. 53 (2008): 293-321.
- https://cwf-fcf.org/en/resources/encyclopedias/fauna/insects/firefly.html
- Firebaugh, Ariel, and Kyle J. Haynes. “Experimental tests of light-pollution impacts on nocturnal insect courtship and dispersal.” Oecologia 182.4 (2016): 1203-1211.
- Cinzano, Pierantonio, Fabio Falchi, and Christopher D. Elvidge. “The first world atlas of the artificial night sky brightness.” Monthly Notices of the Royal Astronomical Society 328.3 (2001): 689-707.
- Gaston, Kevin J., et al. “Reducing the ecological consequences of night‐time light pollution: options and developments.” Journal of Applied Ecology 49.6 (2012): 1256-1266.
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