ZeFrank on the waning of fireflies

April 4, 2025 • 12:30 pm

Here’s a short ZeFrank video on the apparent waning of fireflies, which are luminescent species of beetles in the family Lampyridae. Wikipedia notes as well that fireflies seem to be disappearing worldwide, and there are many reasons why this should be so:

Firefly populations are thought to be declining worldwide. While monitoring data for many regions are scarce, a growing number of anecdotal reports, coupled with several published studies from Europe and Asia, suggest that fireflies are endangered. Recent IUCN Red List assessments for North American fireflies have identified species with heightened extinction risk in the US, with 18 taxa categorized as threatened with extinction.

Fireflies face threats including habitat loss and degradation, light pollution, pesticide use, poor water quality, invasive species, over-collection, and climate change. Firefly tourism, a quickly growing sector of the travel and tourism industry, has also been identified as a potential threat to fireflies and their habitats when not managed appropriately. Like many other organisms, fireflies are directly affected by land-use change (e.g., loss of habitat area and connectivity), which is identified as the main driver of biodiversity changes in terrestrial ecosystems. Pesticides, including insecticides and herbicides, have also been indicated as a likely cause of firefly decline. These chemicals can not only harm fireflies directly but also potentially reduce prey populations and degrade habitat. Light pollution is an especially concerning threat to fireflies. Since the majority of firefly species use bioluminescent courtship signals, they are also sensitive to environmental levels of light and consequently to light pollution.A growing number of studies investigating the effects of artificial light at night on fireflies has shown that light pollution can disrupt fireflies’ courtship signals and even interfere with larval dispersal. Researchers agree that protecting and enhancing firefly habitat is necessary to conserve their populations. Recommendations include reducing or limiting artificial light at night, restoring habitats where threatened species occur, and eliminating unnecessary pesticide use, among many others.

The video describes various ways of monitoring their abundance as well as reprising the causes of decline describe above. When I was a kid, fireflies were abundant during the summer, and we would catch them and put them in jars to make lanterns (we’d let them go afterwards).  Now I can’t remember when I last saw one of these amazing insects. It’s very sad.

I could go on about how they emit light, and the amazing species that flash synchronously, but I’ll leave that ZeFrank in a future video. But if you want to donate, just go to this page of the Xerces Society for Invertebrate Conservation and cough up a few bucks.

 

h/t Matthew Cobb

23 thoughts on “ZeFrank on the waning of fireflies”

  1. Amazing. I have never seen a firefly as we don’t have them here in New Zealand. What wonderful creatures, it would be a shame to lose them.

  2. I read a fascinating paper many years ago. There is very complex physics and chemistry going on that explains how fireflies covert chemical energy to light with so little waste as thermal energy. Truly nature is grand.

  3. Anyone interested in fireflies would do well to read Sara Lewis’s fantastic book “Silent Sparks: The Wondrous World of Fireflies,” published by Princeton University Press. She has a great line in there that I’ve always wanted to modify for my own writing: “If you love fireflies, I wrote this book for you.”

  4. The last time I saw them was when I visited my mother in central Pennsylvania a few summers ago. She lives in a rural area. They seemed to billow up into the air at dusk, all firing in unison. An awesome sight.

    Yes, I’ve read that they are at risk. Firefly tourism! I’ve never heard of such a thing. As a kid growing up in upstate New York I used to collect fireflies and put them in a jar. I wasn’t a tourist. I lived there.

    Luciferin + luciferase = Let there be light!

  5. I am not a firefly expert, but these claims of firefly endangerment sound like other nonsensical claims of species endangerment.

    1a. ‘I don’t see as many fireflies as I use to as a kid.’ Your memory is faulty, because everybody’s memories are faulty. Also, you more distracted now (because everyone is more distracted now).

    1b. Fireflies need the same moist conditions as mosquitoes to lay eggs. Since humans tend to mitigate against mosquitoes right near their houses, they are less likely to see fireflies. This doesn’t mean that there are fewer fireflies, or mosquitoes.

    2a. ‘Endangered species’ A species is considered endangered if its population falls below a certain threshold. This is considered to be true even if that species has thrived for millions of years with a population below that arbitrary threshold. Many new species are discovered each year and are immediately considered to be endangered simply because their observed population is below a certain threshold.

    2b. If a population is considered to be a single species and then for some reason is split into two or more species it is possible/likely that all of the new species will be considered endangered because they have smaller populations. Even if all of these new species are able to interbreed with each other.

    1. So despite your M.S. in Entomology you’ve pretty much ignored the vast amounts of scientific literature documenting the loss of biomass and biodiversity in insects?

      1. No. Would you like to discuss the flaws and inadequacies in that research?

          1. I believe that the etiquette of this website requires you to substantiate (politely) an objection.

    2. There is plenty of evidence of insect population declines worldwide, and especially here in the US. And my memory is not faulty, I know in my youth half a century ago that fireflies were plentiful between the East Coast and the Mississippi River, which I witnessed frequently. Now, there are at best a few dozen on any given night, and often less than that.

    3. Well, I hate to join the pile-on, but every one of your items are laughable. Hasty generalizations and motivated reasoning abounding.
      Please show some links that fail to show species declines.

      1. Strongly agree with Mark. Mr Drabnik has an ideological chip on his shoulder. The evidence for global insect declines (I withhold judgement on the firefly case for now) goes far beyond memories.

  6. Besides the anecdotal claims of species declines for fireflies, other insects, birds, fishes, amphibians, fish, etc., there are numerous studies from around the world that quantitatively show these declines. They involve reproducible collecting methods that are done over an extended period of time, and they show the general decline of populations. Not all species, but high % of them. Just Google “X declining populations”, where X are insects in general, or specific groups, song birds, marine fishes, freshwater fish, etc etc. etc.
    And why not? We can see that that the earth has been progressively terraformed over the decades, with lost of forests and fields to farmland, then to suburbs and cities. It’s not like all those species that require specific conditions will just accommodate around us to continue living in a monoculture of pesticide treated crops and concrete.

  8. Here where I live, a city in eastern Ontario, I have noticed no declines. The firefly season is short but as intense as ever. I wait for it with real anticipation. It always arrives toward the end of July, and it lasts for about two weeks. I make it a point to go out for a good long walk on each of those precious evenings. There’s definitely something magical about them. As kids we called them “lightening bugs.” That’s a better description of the abrupt way they erupt in the darkness.

  10. Fortunately for me, fireflies have not been declining around my house in eastern Australia where I’ve lived for over 20 years. Every August the rainforest behind the house lights up for weeks with the magical flashing of fireflies, a wonderful time I always look forward to.

    There are also luminous mushrooms that occasionally appear as well. And there are glow worms in the area too. But I will never forget the caving trip to New Zealand where we floated down an underground river under a canopy of glow worm lights looking like a galaxy full of stars.

  11. “There’s Candace with a net . . . Oh, sorry, that’s Richard, not Annette.”

    Did anyone else die laughing?

Comments are closed.