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Observation: Photinus pyralis
Primary Observer:
Carl Manthey
Event Date:
2025-08-09
Status:
Verified
Survey
Site Name:
Great Marsh, Elverson, PA
Province/State:
Pennsylvania
Event Date:
2025-08-09
Time of Day:
Night-Time
Start Time:
20:00
End Time:
21:30
Number of Observers:
5
Primary Observer:
Carl Manthey
Additional Observers:
Myrna Villanueva, Melinda Villanueva, Diana Cormack, Meredith Heffner
Target Species Genus:
unknown
Target Species Species:
unknown
Location and Habitat
Location Accuracy (meters):
500-1000
Habitat Type:
Open Freshwater Wetland - Wetland Bog, fen, freshwater marsh
Habitat Type Notes:
Elevation (meters):
150 - 200
Area Searched (hectares):
6
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:
Photinus
Species:
pyralis
Observation Notes:
These big dipper fireflies started flashing at 8:20 and were still flashing at 9:30 when the survey ended.
Specimen Voucher Number:
Flash Behavior
First Flash Time:
20:20
Last Flash Time:
21:30
First Flash Temp (F):
73
Last Flash Temp (F):
71
Flashes in Pattern:
1
Flash Color:
Yellow
Flash Pattern Period:
9 seconds or more
Flash Duration:
0.75 sec
Flash Interval:
8 second or more
Male Height Zone:
Low (0-3 ft), Moderate (3-8 ft), High (over 8 ft)
Flash Location:
At dusk (8:20 PM) the flashes were 0-3 feet off the ground over mowed areas. By 9:00 PM the same flash pattern was observed along treelines, ditches, meadows and soybean fields. Most of the flashes by 9:00 PM were 0-8 feet off the ground but some were higher.
Male Flash Behavior:
All flashes were slow and J shaped. Generally, it was not possible to determine flash intervals because a firefly would seem to emit a single flash and then disappear. In one case 4 flashes were observed over 28 seconds for an approximate 9 second flash interval. Many seconds often passed between seeing a flash from any firefly. While the total number of fireflies observed by the two teams was over 50, the fireflies were by no means abundant. A very rough estimate would be that total flashes observed on August 9 were 1% that observed on June 21 (all species combined).
Female Flash Behavior:
1 thought on “Observation: Photinus pyralis”
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Thanks for submitting this observation and accompanying survey data! Both the appearance of the firefly in the photo (yellow edging on the segment in front of the lanterns; pale scutellum) and the description of the flash behavior align with Photinus pyralis.