The Cricket Thermometer- External Temperature Predictor

DiyaAdhikary, Amity University Kolkata

The very thought that cricket chirps indicate something rather meaningful about our environment other than to simply annoy us with their high-pitched sound is baffling! For some cultures, the chirping of insects holds different meanings- a sign of good luck, rain, something bad, impending illness, or even death. But Science has instead pointed towards an interesting phenomenon, where cricket chirps can be used to measure the outside temperature.

THE DISCOVERY OF A CORRELATION

Physicist Amos Emerson Dolbear analyzed the sound of the cricket (snowy tree cricket) outside his house and observed some sort of correlation between the temperature and the number of cricket chirps. In 1897, Dolbear published an article titled “The Cricket as a Thermometer”. In this article, he mentioned, “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.”

He invented what went on to be known as “Dolbear’s Law”, which is a formula for measuring the approximate outdoor air temperature (in Fahrenheit) using the chirps of a cricket. The Dolbear’s Law is formulated as:

T_F = 50 + [(N₆₀ – 40) / 4]

[Where T_F = Temperature (in Fahrenheit); N₆₀ = Number of Cricket chirps (in 60 seconds)]

And,

T_C = 10 + [(N₆₀ – 40) / 7]

[Where T_C = Temperature (in Celsius); N₆₀ = Number of Cricket chirps (in 60 seconds)]

REASON BEHIND CRICKET CHIRPS

Crickets make the noise by a process called Stridulation, where the rubbing together of their scraper and file produced a unique sound. Male crickets bear a special structure called a scraper on the top of their wings. The sound is produced when they raise their wings at a 45° angle, then draw the one having the scraper across the wrinkles (on the underside) of the other wing. The wrinkles are called a file. Evolutionarily, male crickets chirp to attract females for mating, or to ward off enemies, or to warn other males to stay away from their females.

Depending on the species and the temperature of the environment, the rate of chirping differs significantly. In most species, the chirping rate increases with an increase in the temperature. It’s interesting to know that all crickets chirp synchronously, maintaining the same rate but with a different beat. Hence, the number of chirps can be easily counted (as they will have different beats).

THE FREQUENCY OF CHIRPING VARIES WITH TEMPERATURE

Crickets being insects are cold-blooded hence cannot regulate their internal body temperature of their own free will. Their surrounding temperature controls their internal body temperature as they take up the temperature of their surroundings. The chirping sound is produced due to the rubbing of their scrape and file. This happens as a result of muscle contraction, which in turn occurs due to the set of chemical reactions that take place inside their body. Depending on the speed (rate of the reactions) of these chemical reactions, the chirping frequency tends to vary.

According to the Arrhenius equation, K = Ae (-En/RT), denoting that the rate of a chemical reaction depends on its surrounding temperature.

Hence, during summer when the outside temperature is high, the chemical reactions take place at a faster rate inside the cricket’s body, resulting in more chirps per minute. Again during the winter, when the outside temperature is comparatively much lower, the chemical reactions that take place inside the cricket’s body occur at a much slower rate, thereby resulting in fewer chirps per minute.

DISCREPANCIES OF THIS METHOD:

1. Dolbear did not specify the species of the cricket, however, researchers assumed it to be the snowy tree cricket as the method worked best for this species.
2. The chirping of common field crickets is not reliably correlated to temperature in all cases (variation in rate due to age, mating ritual, and other factors)
3. Dolbears’s formula gives an approximate (within a degree or so) value of outside temperature, hence it lacks accuracy.

CONCLUSION:

In earlier times, humans used to be more connected to nature. Long before the era of industrialisation and modern-day medicine and technology, our wounds were used to heal through natural methods using various naturally occurring substances. We have read about how sailors would find their way by watching the movement of the Sun during the day and by looking at the stars (constellations or heights) at night, much before the invention of the compass. There are several other such examples but all these are now seldom used as technology has over time evolved and better more sophisticated and advanced inventions have replaced them to create the present world we live in. Technology makes our work easier but staying it is also important that it goes hand-in-hand with nature and not against it. After all, staying connected to Mother Nature has always proven to be good for human health. It is rather amazing how nature itself has always created such complex and efficient mechanisms for all kinds of life to occur and continue in complete harmony with one another, and Science is always looking deeper into how mankind can improve and utilize the resources from our surroundings in the environment so that we ensure the continuation of our species on this planet. And just like the chirps of crickets indicating the ambient temperature, we must look towards nature to know about more such extraordinary mechanisms. In this case, Dolbear could successfully produce a link between nature and technology. So the next time we come across the sound of a cricket chirping, we will know that nature has given us crickets in the form of a natural thermometer!

Also read-Do jumping spiders run towards danger?

REFERENCES-

1. Patel Piyush (2020) Dolbear’s Law: Is It Possible To Determine Temperature By Counting Cricket Chirps? ScienceABC. https://www.scienceabc.com/nature/animals/is-it-possible-to-determine-temperature-by-counting-cricket-chirps-the-dolbear-law.html
2. (2020) Sonorous science: Have a cricket tell you the temperature! Scientific American. https://www.scientificamerican.com/article/bring-science-home-cricket-temperature/
3. Snowy Tree Cricket Image- Calibas at English Wikipedia

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