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Observation: Photuris pensylvanica
Primary Observer:
Rosalind Reilly
Event Date:
2025-05-24
Status:
Verified
Survey
Site Name:
Snapper Pool
Province/State:
Virginia
Event Date:
2025-05-24
Time of Day:
Night-Time
Start Time:
21:00
End Time:
22:37
Number of Observers:
4
Primary Observer:
Rosalind Reilly
Additional Observers:
James Reilly, Sam Reilly, Reghan Kerns
Target Species Genus:
Photuris
Target Species Species:
pensylvanica
Location and Habitat
Location Accuracy (meters):
0-25
Habitat Type:
Forested Wetland - Swamp, cedar bog, mangrove
Habitat Type Notes:
Semi-permanent impoundment and wooded wetlands and open marsh through which Jones Creek runs. The wooded wetlands where we saw Photuris pennsylvanica open up into a marsh created by a very old beaver impoundment. The lowland surrounding one side of the marsh is wooded with patchy pools and small open areas thick with vegetation. Openings in the tree cover were the spots where P. pennsylvanicas seemed to congregate more, but they were present all along the wooded wetland border of the marsh where our path led us. Trees: smooth alder (Alnus serrulata), red maple (Acer rubra), Amer. hornbeam (Carpinus caroliniana), Amer. holly (Ilex opaca), river birch (betula nigra), sweetgum (Liquidambar styraciflua).
Elevation (meters):
58
Area Searched (hectares):
3
Artificial Light Sources
Vehicles: No
Street Lights: No
Buildings: No
Street Lights: No
Buildings: No
Artificial Light Types
Sky Glow (diffuse illumination in the sky): No
Light Trespass (light cast on surfaces beyond its intended target): No
Glare (bright light causing visual discomfort): No
Light Trespass (light cast on surfaces beyond its intended target): No
Glare (bright light causing visual discomfort): No
Artificial Light Notes:
Observation
Observation Type:
Flashing
Number Observed:
50+
Genus:
Photuris
Species:
pensylvanica
Observation Notes:
11mm
See notes on habitat
Explanation of png images of flash pattern: My son James took a video with his camera on a tripod, cropped it to the length of one complete flash pattern, then exported as single frames (30 frames/second) into Inkscape, so each rectangle in the image corresponds to 1/30 second. The 2 images are of the same flash, one with brightness enhanced. James suspected that his camera did not pick up the complete length of flashes since it wasn't very sensitive to light. Dot duration = .13 second; Dash duration = 2.77 seconds. Flash interval between dot and dash= 3.33 seconds. Unfortunately we have no figure for flash pattern period because it was so long, we could never be sure we were seeing the same firefly. Possibly slow because of the temperature?
I have a very short video of a single flash train taken with mobile phone, but couldn't upload it.
Specimen Voucher Number:
Flash Behavior
First Flash Time:
21:04
Last Flash Time:
22:00
First Flash Temp (F):
63
Last Flash Temp (F):
59
Flashes in Pattern:
2
Flash Color:
Unknown
Flash Pattern Period:
not determined
Flash Duration:
dot=.13; dash=2.77
Flash Interval:
3.33 between dot & dash
Male Height Zone:
Low (0-3 ft), Moderate (3-8 ft)
Flash Location:
Location was the area surrounding a small pool where the woods give way to more open space dense with vegetation. Ground is very wet. Some flashes very low to ground, probably perched in vegetation. Some traveling flashes knee-height to head height, moving slowly. I will upload daytime picture later.
Male Flash Behavior:
Explanation of png images of flash pattern: Video was cropped to the length of one complete flash pattern, then exported into Inkscape as single frames (30 frames/second), so each rectangle in the image corresponds to 1/30 second. Dot duration = .13 second; Dash duration = 2.77 seconds. Flash interval between dot and dash= 3.33 seconds.
Unfortunately we have no figure for flash pattern period. The time from one double flash to the next was so long, we could never be sure we were seeing the same firefly, nor could we predict where it would be next.
Female Flash Behavior:
1 thought on “Observation: Photuris pensylvanica”
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Great observation, and very nice documentation! Very neat how you captured the dot dash flash pattern with the video stills.
I am verifying this as Photuris pensylvanica, based on the mid-Atlantic, wetland locality; the relatively small size; the dark hind coxae; and the dot-dash flash pattern. This is with the caveat that there is still a lot we don’t know about species delineations in this species complex, and the further you stray from the type locality and habitat, the less confident you can be when putting names to Photuris.