Observation: Pyractomena borealis
Primary Observer:
Stephanie Shepherd
Event Date:
2026-05-04
Status:
Verified
Survey
Site Name:
McCoy Wildlife Area
Province/State:
Iowa
Event Date:
2026-05-04
Time of Day:
Night-Time
Start Time:
20:40
End Time:
21:58
Number of Observers:
5
Primary Observer:
Stephanie Shepherd
Additional Observers:
Riggs Wilson, Ava Stevens, Yuanwu Wang, Other
target_species_genus:
pyractomena
target_species_species:
borealis
Location and Habitat
Location Accuracy (meters):
0-25
Habitat Type:
Woodland/Forest - Trees dominant, and in the over-story
Habitat Type Notes:
The McCoy Wildlife Area has a mix of habitats, including prairie, wetland, ponds, cropfield, upland and riparian forest but the dominant vegetation where fireflies were most notable was deciduous forest with a thick understory.
Elevation (meters):
325
Area Searched (hectares):
3
Artificial Light Sources
Vehicles: No
Street Lights: No
Buildings: Yes
Street Lights: No
Buildings: Yes
Artificial Light Types
Sky Glow (diffuse illumination in the sky): Yes
Light Trespass (light cast on surfaces beyond its intended target): Yes
Glare (bright light causing visual discomfort): No
Light Trespass (light cast on surfaces beyond its intended target): Yes
Glare (bright light causing visual discomfort): No
Artificial Light Notes:
Skyglow from the town of Boone and the town of Ames. A little light trespass at the start of the survey from nearby office building.
Observation
Observation Type:
With Flash Data
Number Observed:
50+
genus:
pyractomena
Species:
borealis
Observation Notes:
This photos represent 2 individuals. Individual 1 was perched on a shrub and was caught by hand. It was not flashing at the time. Individual 2 was caught in the air after flashing about 7' above the ground. Most individuals observed were in treetops flashing or similar in height to this one. They were concentrated in the forest eddges but a few of the adjacent crop field and trail.
Specimen Voucher Number:
Flash Behavior
First Flash Time:
20:45
Last Flash Time:
21:58
First Flash Temp (F):
62
Last Flash Temp (F):
56.9
Flashes in Pattern:
1
Flash Color:
Unknown
Flash Pattern Period:
30
Flash Duration:
1
Flash Interval:
3-4
Male Height Zone:
High (over 8 ft)
Flash Location:
Mostly towards the top of trees or while flying around 8-9 feet.
Male Flash Behavior:
Single flashes that started sparsely (only a few individuals flashing) at the beginning of the survey but became denser (many individuals flashing) about 45 minutes to an hour post sunset. we struggled to lock in and get a sense of the flash pattern period. Yuanwu was able to follow 1 for 10 flashes at 3-4 second intervals. Flashes were very short and Yuanwu commented that they were dimmer than other species. Color was also a challenge. Most looked white to green but a few were orange.
Female Flash Behavior:
NA
1 thought on “Observation: Pyractomena borealis”
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Very nicely-documented observation of Pyractomena borealis! The seasonal timing, habitat and size and appearance in your photos are all a good match for the species.
One note about flash pattern terminology (which I realize is not intuitive!): In a single-flashing species with quick flashes like P. borealis, the flash pattern period and flash interval are essentially the same. Flash pattern period is the time between the start of one flash pattern and when it next repeats. There’s a flash pattern diagram on the data sheet with reminders about what the different terms refer to. Flash duration is difficult to actually measure, so it’s fine to enter “brief”, “quick” or “<0.5 seconds" in this field. The duration of Pyractomena borealis flashes in the literature is about a quarter second-- a one-second duration is actually pretty long for a firefly, appearing almost more like a glow than a blink/flash.