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Dot-dash firefly

Photuris pensylvanica
Firefly icon. (Natasha Sinegina, CC-BY-4.0 /
U.S. State
New Jersey
New York
Washington D.C.
Life History

Activity Period and Flash Signal

Adults are active in June and July. Males emit a characteristic greenish dot-dash flash pattern, comprised of a quick flash followed by a long flash that lasts up to three seconds.


The dot-dash firefly is found in DC, Delaware, Maryland, New Jersey, New York, and Pennsylvania.

Habitat Associations

This species is a habitat specialist associated with high quality tidal and non-tidal freshwater wetlands, such as shrub and forest acidic seepage swamps, emergent marshes, fens, fresh-water tide marshes, and floodplains.

Conservation Status

The main threat to this species is habitat degradation due to sea-level rise, invasion of the non-native plant common reed (Phragmites australis), and development.

Conservation Needs
  • We need to know more about the distribution of this species. Please check out the Firefly Atlas to help us track and conserve this threatened firefly.
  • Turn off your outdoor lights at night so the lights of this firefly aren’t diminished by light pollution. You can read more about firefly-friendly lighting in our fact sheet.
  • Avoid pesticide use, which could harm this firefly, its habitat, or its prey.
  • More research on population size, trend, and life history is needed for this species.
Prepared By

Candace Fallon, The Xerces Society for Invertebrate Conservation, based on the IUCN Red List assessment