The light from Photuris pennsylvanica was measured to be 552 nm (green-yellow) while Pyrophorus plagiophthalamus was measured to emit light at 582 nm (orange) in the ventral organ.
On April 10, 1974, Governor Milton J. Shapp signed their bill, making the Pennsylvania firefly their state's official insect.
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Its primary color is black, but it has two bright-red eyespots on its thorax, as well as yellow edging on its thorax and wing case.