Observation: Photinus obscurellus
Primary Observer:
Brandie Dunn
Event Date:
2025-06-20
Status:
Verified
Survey
Site Name:
Undisclosed
Province/State:
Illinois
Event Date:
2025-06-20
Time of Day:
Night-Time
Start Time:
20:35
End Time:
22:00
Number of Observers:
2
Primary Observer:
Brandie Dunn
Additional Observers:
Sylvia Dunn
target_species_genus:
unknown
target_species_species:
unknown
Location and Habitat
Location Accuracy (meters):
0-25
Habitat Type:
Open Freshwater Wetland - Wetland Bog, fen, freshwater marsh
Habitat Type Notes:
We observed activity in and around the fen, as well as in and along the neighboring forest edge.
Elevation (meters):
820
Area Searched (hectares):
.166
Artificial Light Sources
Vehicles: Yes
Street Lights: No
Buildings: No
Street Lights: No
Buildings: No
Artificial Light Types
Sky Glow (diffuse illumination in the sky): Yes
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:
With Flash Data
Number Observed:
11-50
genus:
photinus
Species:
obscurellus
Observation Notes:
Most individuals appear to start out by flashing lower to the ground on vegetation. The timing between their triple flash would vary, but it was more lengthy compared to other species observed. This individual was 13mm. They all appeared to be concentrated in the wetland area. Unfortunately, we didn't not take a final temperature reading at the exact spot we were observing activity. (On a subsequent survey on 6/23/25, it was noted that this species wasn't displaying as actively as survey's earlier in the month of June.)
Specimen Voucher Number:
Flash Behavior
First Flash Time:
21:06
Last Flash Time:
22:00
First Flash Temp (F):
72
Last Flash Temp (F):
75
Flashes in Pattern:
3
Flash Color:
Yellow
Flash Pattern Period:
10
Flash Duration:
.5
Flash Interval:
.3
Male Height Zone:
Low (0-3 ft)
Flash Location:
In and around the skunk cabbage and other vegetation in wetland.
Male Flash Behavior:
He would flash 3 times and there would be a lengthy stretch before he would repeat it.
Female Flash Behavior:
1 thought on “Observation: Photinus obscurellus”
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Again, nice documentation of this firefly! Based on the flash pattern and appearance (narrow form, dark elytra, pointed dark pygidium), this is definitely in the “ardens group,” which is represented in Illinois by Photinus ardens, Photinus consimilis, and Photinus obscurellus. I think this is Photinus obscurellus based on the short (0.3 second) interval between the pulses and the fact that you found an individual with much darker maroon on the pronotum earlier in the season.
Page 39 of this guide to fireflies of Ontario has a nice comparison between Photinus ardens and Photinus obscurellus, which were once considered to be the same species.