Identifying fireflies is very difficult, even at the best of times, because many fireflies look exactly alike. As with many small insects, the only sure way to identify them is to compare some of their internal organs. This is a technique that goes beyond the scope of our study, and we do not ask our members to identify the fireflies they are seeing.
However, since many fireflies communicate using flash patterns unique to each species, it is often possible to identify a firefly by its pattern. With patient observation, you can start to recognize the different fireflies in your habitat. Then, use this flash chart to identify the patterns you are seeing.
Download the Chart (PDF)
Notes About the Chart
Although using the chart to identify fireflies may sound like a simple process, please be aware of the following:
The Chart Is Incomplete
There are approximately 150 species of fireflies in the United States, and the chart lists only a small percentage of them. It contains some Photinus, a few Pyractomena, and no Photuris . We will update the chart as more information becomes available, but for now, it is incomplete.
Flash Rates Change With Temperature
As the temperature drops, the flash rate slows down. For instance, male Photinus aquilonius fireflies flash once every 5 seconds at 70°, and once every 11 seconds at 54°. Data for flash rates at different temperatures is scarce, so you will have to guess how much to adjust the flash rates to compensate for any difference in temperature from what you see listed in the chart.
Not Each Firefly On The Chart Will Live In Your Area
It is possible that you might match your firefly to a flash pattern on the chart only to find out that the firefly doesn't live in your area. Unfortunately, range maps do not exist for many fireflies, but some can be found for Photinus fireflies in the pamphlet, "Studies on the Flash Communication System in Photinus Fireflies" by Dr. James Lloyd. Much of the information on the flash chart comes from this pamphlet; it contains lots of good information on over 20 species of Photinus fireflies.
Photuris Fireflies Will Often Imitate Other Species
Some Photuris females prey on other fireflies, imitating the female of their prey species in order to lure males close enough to grab and eat. The only way to be sure that you are looking at a Photinus or Pyractomena firefly — and not an imitating Photuris -- is to catch it and identify it visually.
Learn more about safe handling of fireflies.
How to Use the Chart
In spite of these difficulties, it is fun use the flash chart to identify the fireflies in your habitat by their flash pattern.
To identify your fireflies, follow these few steps:
- Time the flash pattern of a male firefly with a stopwatch. He will usually be flying. Record the timing of the pattern.
- Find a perched female that is responding to his signal and time that with a stopwatch. Record her timing.
- Catch both the male and female to determine whether they are Photinus or Pyractomena. Make sure you are not looking at an imposter Photuris firefly.
Review types of fireflies.
- Find the flash pattern on the chart that most closely resembles your observation, taking into account the difference in temperature.
- If you have identified your firefly as a Photinus sp., check the range maps in Dr. Lloyd's report to make sure that firefly lives in your area.
Download the Chart (PDF)
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