Fun Science: The Backyard Cricket Thermometer

The loud crickets chirping in unison tonight reminded me of A. E. Dolbear’s observation that crickets can tell you the current temperature.  According to his classic 1881 communication:

T = 50 + (N-40)/4

where N is the number of field cricket chirps per minute, and T is the temperature in Fahrenheit.  An easier to remember equivalent is

T = N + 40

where, in this case, N is the number of chirps in 15 seconds.

I gave it a try tonight.  I counted 91.7 ± 2.1 chirps per minute, yielding a calculated temperature of 62.9 ± 0.5 degrees.  The actual reading on the thermometer outside?  61 degrees.  Pretty good accuracy, and no instrumentation required.

Bonus science trivia:  All nearby crickets of the same species will synchronize their chirping — despite the fact that the males are actually competing with each other for mates.

Extra bonus science trivia: The chirping rate of crickets (and many activities of cold blooded creatures) actually follows the Arrhenius equation for the temperature dependence of chemical reaction rates.  The chirping rate is a function of temperature because of the underlying biochemical reactions that give the cricket the energy it needs to chirp.

[Reposted from 8/16/13.  Outside my window, tonight’s chirp count was 104/min, or 66 degrees, and the actual thermometer reading was 64.]

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