What kind of firefly am I?

People have been posting their firefly photos to the community science site iNaturalist – it’s wonderful! Inspired by everyone else’s fabulous shots (I wish I could do that with my iPhone), here’s a short key to help you distinguish six of the most common firefly genera found in the U.S. Give it a try & let me know what you think in the comments below!

1a. Active during evening or nighttime, abdomen with a lantern, wing covers without pale borders ……. Go to #2

1b. Active during daytime, abdomen without a lantern, wing covers with pale borders ……. Go to #4

2a. Pronotum (head shield) with a raised ridge running down the midline & angular outline ….. I am Pyractomena (18 species)

2b. Pronotum without a raised ridge running down the midline (could be flat or grooved), outline more round in shape ……. Go to #3

3a. Legs are long  (almost as long as the wing covers) and slender; when beetle is viewed from the side, the front corner of each wing cover curls smoothly under, making its shoulders look hunched ….  I am Photuris (73 species)

3b. Legs are short (less than half as long as the wing covers) and stout; when shoulder is viewed from the side, the wing cover’s sharp edge makes a straight line …. I am Photinus (48 species)

4a. Antennae inconspicuous; threadlike and short …. Go to #5

4b. Antennae conspicuous; flattened, long and saw-toothed I am Lucidota (4 species)

5a. Largish beetle (length 1cm or more)I am Ellychnia (12 species)

5b. Tiny beetle (length ≤ 5 mm) …. I am Pyropyga (4 species)

Other Online Resources

Key to Fireflies of Ontario by Stephen Luk, Stephen Marshall and Marc Branham (2011)

Photinus flash codes

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