On Tuesday June 29th 2023, Don Salvatore, former science educator at Boston’s Museum of Science for over 35 years, offered a glimpse into the world of fireflies and the (sometimes) surprising interactions that take place in a firefly meadow. You can watch the presentation here or at the end of this summary.
Most of us know and love fireflies — especially here in New England where they are a common midsummer sight — yet we know very little about them. Even the name “firefly” is a bit of a misnomer, as is the name “lightning bug,” because these glowing insects are actually beetles. Not all fireflies look like we would expect them to — flightless glow worms and some non-luminescent diurnal beetles are also part of the firefly family. However, all fireflies do glow at some point in their lives. The eggs, larvae, and pupae of fireflies all glow regardless of their adult form.
The creatures you imagine when you think of fireflies are probably those which fly around after dark, blinking their glowing abdomen. These are male fireflies participating in a mating ritual, taking flight and flashing in precise patterns in hopes of attracting a female mate. Their female counterparts stay on the ground and flash in response, revealing their location to interested males. But competition is stiff for mating-hopeful males. For each female firefly, there are many more male fireflies, all of whom are vying for her attention.
Not every firefly we see is the same. There are many species of fireflies in Maine, adding a layer of complexity to this high-stakes mating display. Each species is only interested in mating with others of the same species and the primary way they identify their own kind is through species-specific flashing patterns.
Some particularly clever fireflies use this mating confusion to their advantage. There are three genera of flashing fireflies in Maine – Photinus, Pyractomena, and Photuris. (There are also three genera of non-flashing daytime fireflies in Maine.) The genera Photinus and Pyractomena are relatively small, while fireflies of the genus Photuris are twice their size and their primary predator. While we imagine all that delightful flashing in the meadow as something comparable to a bar full of funloving fireflies looking for love, there are sinister activities at work as well!
To lure smaller male fireflies in, a hungry female Photuris will copy the flashing patterns of a female Photinus in the hope that a Photinus male will rush over and become a tasty meal. However, some male Photinus are aware of this ploy and will take time to check out the flashing female before rushing in. If the males notice any errors in the Photinus flash pattern, they will stay away.
To further complicate matters, other intriguing behaviors have been observed. A Photinus male has been seen botching a Photinus flash pattern himself, presumably pretending to be a Photuris female impersonating a Photinus female. The theory of this behavior is that other Photinus males will see this and fly away, leaving the trickster with less competition for real Photinus female mates. (So, if you thought the human dating scene was complicated….)
Photuris males also participate in the Photuris-Photinus masquerading. Female Photuris fireflies are often more interested in finding Photinus males to eat than with mating, which is troublesome for desperate Photuris males. To get around this, some Photuris males will imitate the patterns of Photinus males in order to get close to the hungry Photuris females. In doing so, they are hoping the female will mate with them once she realizes her prospective Photinus prey is actually a viable Photuris mate.
But why are Photuris females so interested in eating Photinus males, especially considering that adult fireflies don’t generally eat? The answer is — they do it to protect themselves. Fireflies are both slow-moving and very visible at night, making them easy to catch. Some fireflies are undesirable prey because they are poisonous. However, female Photuris fireflies do not have the toxin that makes them poisonous, so they eat Photinus fireflies to obtain it. Because, “You are what you eat!”
Firefly populations appear to be waning in the Northeast, likely due to three main factors: habitat loss, confusion from light pollution, and pesticide use. Many fireflies favor wetlands and moist meadows, desiring long grasses and plants to live in and moisture-dependent prey such as slugs and snails to feed on. They are also sensitive to pesticides which kill them and their prey and can linger in their habitats for a long time. To protect firefly populations, we can f replaced manicured, chemically-treated lawns in favor of yards full of diverse native plants and grasses. We can also participate in citizen science to help scientists better understand firefly population trends . Those interested in learning more about how to participate and see the data can go to Firefly Watch, an initiative started by Don to monitor firefly activity nationwide using citizen scientist observations.
If you want to know more about fireflies, the podcast Ologies has a fantastic episode in which they interview Sara Lewis (“Sparklebuttology”) that you can access here. And try your hand at identifying fireflies by their flash pattern, using this chart.
Books referenced in presentation:
Silent Sparks by Sara Lewis (2016)
Fireflies, Glowworms, and Lightning Bugs by Lynn Faust (2017)
There’s a lot more to glean from Don’s presentation, which you can watch in its entirety below.