Using Crickets as Thermometers
The wing-sawing repertoire of crickets runs deep and comprises tunes suited to every occasion, from attracting mates to announcing danger [source: Library of Congress]. But did you know that their chirping also bears a direct relation to air temperature?
Crickets chirp faster in warmer conditions and more slowly as the air turns more frigid. In some species, such as Oecanthus fultoni, aka the "thermometer cricket," chirp rate and temperature share a strikingly direct and linear relationship (within a specific temperature range from 18 to 32 C, or 64 to 90 F). In other species, the connection is less pronounced, but the rule generally works [source: Doherty].
Indeed, research has shown that you can calculate air temperature by counting nearby cricket clicks and entering them into a simple formula. In an 1897 edition of The American Naturalist, A. E. Dolbear derived the formula as T = (50 + N – 40) / 4, where T = temperature (F) and N = chirp rate per minute [source: Dolbear]. "The Farmer's Almanac" says to count the number of chirps occurring in 14 seconds, and then add 40 to get temperature in Fahrenheit. For Celsius, it says to count number of chirps in 25 seconds, divide by 3, and then add 4 [source: Farmer's Almanac].
So the next time crickets keep you awake, don't count sheep -- calculate air temperature.