18 hours ago
22 chirps = 17°C?: How crickets became nature's living thermometers
Did you know that the cricket chirp is nature's indicator of the weather? According to the official website of Reconnect With Nature, American scientist Amos Dolbear first described this quirk of nature in 1897. In his paper 'The Cricket as a Thermometer,' he observed that the muscles crickets use to chirp move more easily in warmer temperatures than they do in cool weather. This correlation was so reliable that he was able to write a formula that connected ambient temperature to cricket chirp rates — popularly known as the Dolbear's law.
According to the National Oceanic and Atmospheric Administration, the Dolbear's law states that temperature in degrees Fahrenheit is roughly equal to the number of cricket chirps in 15 seconds plus 40.
Here's some cricket math: If you count 22 cricket chirps in 15 seconds, it is roughly 62 degree Fahrenheit (or 16.67 degree Celsius), because 22+40=62. If you count 35 chirps, it's about 75 degrees out (or 23.89 degree Celsius), because 35+40=75. Based on these simple equations, you can see that crickets chirp faster in warmer temperatures than they do in lower temperatures.
The reason a cricket's chirp rate changes with the temperature is because they are cold-blooded, or ectothermic, meaning their body temperature is the same as that of their external environment. Chirping requires their muscles to contract, and temperature is a factor in how quickly the chemical reaction necessary for muscle contraction can occur. Muscles contract faster in warmer temperatures, allowing them to chirp at a more frequent pace.
According to the Reconnect With Nature website, it is believed, however, that Dolbear was listening to a snowy tree cricket, a species that has earned itself the nickname 'thermometer cricket.'
While cricket math is a useful indicator of the temperature, keep in mind the crickets generally don't chirp when the temperature is below 55 degrees Fahrenheit or above 100 degrees Fahrenheit, according to the University of Nebraska-Lincoln. Plus a cricket's chirping rate can be affected by hunger, age, mating success and competition from other male crickets.
Although we can derive useful, if not exactly precise, information about the temperature from a cricket's chirps, that's not the point of the racket. The real reason crickets chirp is because the males attract a mate.
The process of chirping is called stridulation, and crickets create their signature sound by rubbing their wings together. When they want to chirp, they raise their wings, and a structure called a scraper on one wing moves across a structure called a file on the other wing. The process of rubbing these two structures together is similar to what happens when you run a finger along the teeth of a fine-tooth comb.
