Why is firefly courtship dangerous?
By Chelsie Vandaveer
April 16, 2003
Fireflies or lightning bugs are beetles in the family, Lampyridae. Although not all lampyrids can bioluminesce, the best known are those that court their mates by flash communication in the twilight hours of summer. Two genera, Photinus [fo tin' us] and Photuris [fo tur' is], are common in North America.
The courtship of Photinus fireflies generally consists of females sitting stationary on the ground or in low vegetation and the males flying low and signaling. His signals and her responses, 'firefly chit-chat', are species-specific. If they are both the same species and the introduction goes well, the male will land and approach the female.
Photuris fireflies, of which there are thirteen or so species, are mimics of the Photinus fireflies. Photuris females answer the signals of the male Photinus fireflies. He lands believing he has a date, not realizing that it is a dinner-date and he's the main course. (A Review of Predation in Photuris, and its Effects on the Evolution of Flash Signaling in Other New World Fireflies, Hollend Stous, 1997, Colorado State)
A team of researchers at Cornell--Thomas Eisner, Michael Goetz, David Hill, Scott Smedley, and Jerrold Meinwald--found that Photinus fireflies are protected from predators by lucibufagins, steroidal pyrones similar to the toxins produced by Bufo toads and the cardiotoxins produced by some plants. Photinus fireflies will ooze a droplet or two of their toxic blood when under attack. Spiders, beetles, birds, and other predators abandon a Photinus meal. (Lured and Liquidated, Thomas Eisner, 1997, Cornell University Science News)
Photuris fireflies do not produce lucibufagins and are defenseless against predation. When a female Photuris has eaten a male Photinus, she gains the protective chemical. But the chemical does not simply protect her. According to Andres Gonzalez and Thomas Eisner, the female Photuris passes the protection on to her eggs. (Chemical Egg Defense in Photuris "Femme-Fatales", Gonzalez and Eisner, 1999, International Society of Chemical Ecology)
To learn more about the Lampyridae, their mating rituals, mimicry, and chemical defenses, there are two great articles on the internet:
Hollend Stous has an in-depth article on firefly behavior, A Review of Predation in Photuris, and its Effects on the Evolution of Flash Signaling in Other New World Fireflies. To read his article, click on the link:
http://www.colostate.edu/Depts/Entomology/courses/en507/papers_1997/stous.html
Cornell University Science News has a press release, Lured and Liquidated, with photographs of a spider deterred by the Photinus firefly:
http://www.news.cornell.edu/releases/Aug97/luredandliquidated.hrs.html
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