Sunlight & Seasons

Firefly Decoder


Unlocking the Code

Firefly expert Marc Branham of New York's American Museum of Natural History (and Ohio State University) wondered what was it in a specific flash pattern that was attractive to females. He studied this question by videotaping and analyzing fireflies' flash patterns. As a further step, he and John Mircle and Michael Greenfield of the University of Kansas also developed a computerized device that simulated the male flash pattern, so that he could observe the females' responses.

Marc's research showed that a female firefly's responding or not responding to a male's flash may depend on the rate or speed of the male's flashes. His computer testing showed to the females simulated male flashes at average rates, and also flashes that were at above-average and below-average rates too. He even created some above-average and below-average rates that were beyond the rates that fireflies could produce naturally.

I'm Not Giving You the Time of Day!
The average rate of flashing in the species studied (Photinus consimilis), he found, was 3.3 flashes per second. (Other species should be different.) At the naturally high rate of 3.6 flashes per second, Marc said love was in the air; and the artificially high rate of 4.3 flashes per second drove the females wild. At the naturally below average rate of 2.8 flashes per second and the artificially low rate of 2.5 flashes per second, the bugs and the computer "couldn't get the time of day" from the females.


Click Image to see Flash
Credit: Dr. Patrick C. Hickey
University of Edinburgh, Scotland, UK.

What does a faster flash rate tell a female about a male? Marc theorizes that:

 


"I think that high flash rates might be an indicator of high male quality (good genes) i.e., no parasites, etc. This, however, is very difficult to test and generally requires rearing (raising) the animal being studied - and fireflies are very difficult to raise because they are predacious."

Lights Out Please!

Credit: J.E. Lloyd,Univ. of Florida

If you were a male firefly, what surrounding conditions would you want in order to get your flash pattern seen? You would want to have extra light reduced or eliminated! A firefly's ability to see other fireflies' flashes may be impaired if there is too much surrounding light. Think about it, it would be like trying to see a flashlight in the daylight. Also, it seems that some firefly species may not even flash at all if there is too much light. As Marc explains it:

 


"many firefly species are active only during a certain period of the evening. These insects determine when they will flash (i.e., the time of night) by the intensity of ambient light. This is why you don't see many fireflies flashing on clear nights when the moon is full."


Try This!
Make a Diagram to show the different subsets of male firefly flash rates described by scientist Marc Branham. Use colored pens or pencils to show which rates the females responded to. Use a different color for each level of response, i.e. no response, some response, most response.

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