ROCHESTER, N.Y. (WROC) — Have you ever stood in a field on a warm summer evening, when all of a sudden you see tiny bright lights popping up in your field of view in the dark? Those glowing bugs signal the unofficial start of the season!

Fireflies, also known as lightning bugs (or even glowworms) are a part of the Lampyridae family that produce a glowing light from their abdomens. It’s not magic—their famous glow by is an example of bioluminescence, produced by the mixing of natural chemical compounds their bodies produce.

Fireflies, lightning bugs, or both?

It’s thought that the name attached to the insect could have something to do with which natural phenomena occur most frequently in that region. Check out the regional map from author Josh Katz below:

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There’s a theory that exists that people who call the insects “lightning bugs” reside in an area with the most frequent lightning strikes on average. Take a look at the average U.S. total lightning density map from 2015-2019 per county below:

Image courtesy: VAISALA annual lightning report 2020

The purple and blue colors within the Midwest and Southern U.S. are where thunderstorms are most frequent, lining up where the majority of people say “lightning bugs.” The data below about wildfire activity by county is a little bit older, but still shows the regional differences based on who typically sees the most wildfires.

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As far as fireflies go, the region that mostly refers to them by that name sees significantly greater wildfire activity. See the pattern? It’s not conclusive and could just be a coincidence!

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How does they light up?

Bioluminescence is a process that takes place from a chemical reaction that produces energy in the form of light. In order for this to happen, you need the reaction between the air (oxygen) and the organic compound luciferin, which is found in the bug’s abdomens to take place.

The enzyme luciferase acts on luciferin in the presence of magnesium ions, a chemical called adenosine triphosphate, and oxygen. The resulting light produces little to no heat, so it’s actually a very efficient way to produce light energy!

Weather and fireflies

These insects love the warm, humid weather. This is why they are sometimes referred to as the “muggy bugs,” and why summertime is the perfect time of year where they like to come out ranging from mid-May to mid-June. This is when temperatures start to warm up enough for the larvae to emerge from the ground.

Weather plays a role not only when during the year you see them, but in how frequently you see the flashes of light in a given night. When overnight temperatures are warm, fireflies can thrive with an abundance of flashes of light, but on nights where temperatures drop into the 50s for example, their flashes occur a lot slower and less frequent. This happens because fireflies are cold-blooded, which means they require and depend on warmth in their environment to function on a daily basis.

Depending on the weather, these insects will appear sooner depending on if we had a mild winter or not. If the winter is mild, odds are you’ll have a much larger firefly population since there’s a greater likelihood of the larvae having survived the cold winter.

Wet springs are also helpful to fireflies since the larvae feed on things like snails, slugs, and pill bugs, which all come out when it rains. The more food available means the more fireflies that thrive! If the weather is too hot or dry, this can be detrimental to the larvae causing them to die before they can hatch, or cause a delay in their emergence. The flickering light of these insects isn’t just random in nature but is used to attract mates and ward off predators.

Firefly fun facts 

  • There are more than 2,000 types of firefly species
  • They are not actually “flies,” they’re beetles
  • Not all species of fireflies glow
  • Firefly blood contains a defensive steroid called lucibufagins, which is poisonous to predators
  • They are not safe for pets to eat
  • Some fireflies are cannibals 
  • The color of light that you see (either yellow or green) depends on the polarity of molecules produced, and the wavelength of light—yellow and green fall in the middle of the ultraviolet and infrared light spectrum