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Spring 2011

Urban Jungle

The changing natural world at our doorsteps | Illustration and text by Patterson Clark      

June 14, 2011

Firefly falls for femme fatale

During a June dusk, common eastern fireflies (Photinus) emerge from their daytime hiding places in the grass. Males climb out to the tips of vegetation, take flight and begin blinking their greenish yellow lanterns for a third of a second every 5 1/2 seconds. Females stay grounded but observe the performances, waiting two seconds after spotting a male's flash before blinking their own lanterns, signaling a receptiveness to mating.

But some males responding to a come-hither beacon may find themselves face to face with a deadly seductress. Pennsylvania firefly (Photuris) females can imitate the receptive flash of their Photinus cousins, drawing in males of that species, which they will try to kill and eat.

But lady Photuris is after more than just a meal. Her species lacks a compound that Photinus has in its blood. After feeding on a Photinus male, a Photuris female will be endowed with her victim's chemical repellents, which will prevent her from being devoured by spiders and birds.

Sources: Cornell University; University of Michigan

common eastern firefly, Photinus pyralis