Insects

You Can Tell The Temperature From Cricket Chirps, Thanks To Dolbear's Law

Physicist Amos Emerson Dolbear is most famous for a small report he published in an 1897 issue of the American Naturalist that included these words: "The rate of [a cricket's] chirp seems to be entirely determined by temperature and this to such a degree that one may easily compute the temperature when the number of chirps per minute is known." This came to be known as Dolbear's Law.

Why Are Cricket Chirps Dependent on Temperature?

All cold-blooded creatures, crickets included, follow the Arrhenius equation, which states that the rate of a chemical reaction depends on the surrounding temperature. Muscle contractions, like those that let a cricket chirp, occur through chemical reactions taking place in the body. So the colder it is outside, the slower the chemical reactions in a cricket's muscles, and the less frequent its chirps. When it's hotter outside, a cricket chirps more frequently.

The fact that crickets have no mechanism for controlling the internal temperature of their bodies (like humans do) means that they are not physically capable of changing the frequency of their chirps on their own. This correlation is predictable enough for you to accurately determine the temperature outside the moment you wake up, without even opening your eyes:

Degrees Fahrenheit = 50 + (chirps per minute - 40)/4

Who Was Amos Emerson Dolbear?

Amos Emerson Dolbear was a highly accomplished physicist and inventor who, had two key moments in his life gone slightly differently, could have become a household name like Thomas Edison or Samuel Morse. He invented the first telephone receiver in 1865, 11 years before Alexander Graham Bell, but failed to observe the correct patent office formalities and couldn't prove his claim when Bell applied for the same patent later on.

Dolbear attempted to secure the patent, but lost the case before the United States Supreme Court in 1888. To be fair, Dolbear's case against Bell was just one of more than six hundred lawsuits against the Bell Telephone Company, which historians of American patent law call The Telephone Cases. At the time it was obvious that telephones were the next big thing, and major interests like Western Union (the world's biggest communications company at the time, thanks to the telegraph) wanted it.

Although Dolbear learned his lesson and made sure to patent his 1882 invention for sending wireless telegraph signals through the Earth, the patent was bought out in 1899 and used to unsuccessfully attack Guglielmo Marconi's later patent for atmopheric electromagnetic radio transmission. The presiding judge decided that Dolbear's underground wireless technology was fundamentally different than Marconi's, and threw out the case. Although the one lasting contribution to carry Dolbear's name through the ages is an obscure law about cricket chirps, he was recognized for his scientific contributions during his life, earning prestigious achievement awards at both the Paris Exhibition of 1881 and the Great Exhibition  at London's Crystal Palace in 1882. He authored several well-received books and earned a professorship at Bethany College in West Virginia.

Can Crickets Really Tell The Temperature?

We've known they can for more than a century.

Written by Austin Jesse Mitchell December 16, 2016

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