If I had to wager a guess, I’d bet that you likely don’t have strong feelings about crickets. In fact, you probably don’t give crickets much thought at all (unless a cricket has found its way inside your house and has kept you awake at night with its chirping).

Well, I’m here to tell you that there’s something about crickets that’s incredibly cool: you can use crickets to determine the temperature!!!

Yes, I know it’s easy to know the temperature these days by simply glancing at your phone or car dashboard.  We even live in a remarkable time when one can simply ask the friendly, ever-waiting household assistant (Google Home, Alexa, etc.) and be informed of not only the temperature, but also the chance for rain. But well before smartphones and wireless assistants were en vogue, crickets have been broadcasting the temperature.  

How do they do it? Read on to find out.

How and Why Do Crickets Chirp?

Crickets chirp through stridulation: the process of making sound by rubbing two body parts together. Despite what you may have heard, crickets don’t  chirp by rubbing their legs together. Instead, they use a special structure on the top of their wings (called a scraper) to rub the wrinkles on the underside of the other wing.

Watch this video and see for yourself that a cricket chirps by rubbing its wings, not its legs.

There are at least three reasons why crickets chirp.  In general, only male crickets chirp and the primary reason for the chirp is to attract a mate (much like the flash of a firefly).  Crickets also chirp to intimidate other males of the species or to sound an alarm if a predator is nearby.

What is the Relationship Between Crickets and Temperature?

Humans and other mammals are warm-blooded.  We are able to keep our bodies at a constant temperature regardless of how warm or cold our environment is.  

Not so with crickets.  Crickets are cold-blooded and take on the temperature of their environment.  (So are reptiles by the way. This is why you’ll often find a snake, turtle, or alligator sunning itself when it’s cold outside). The chemical reactions that power many biological processes require a certain level of energy to take place. Heat is a form of energy, and thus temperature has a direct effect on how well these biological processes can take place for cold-blooded creatures.

The muscle contractions that allow a cricket to chirp rely on temperature-sensitive chemical reactions. Consequently, the frequency of a cricket’s chirp is dependent on the temperature. A cricket is not able to chirp as frequently at cooler temperatures as it is at warmer temperatures.

Dolbear’s Law

Physicist Amos Dolbear is credited with discovering the curious relationship between a cricket’s chirp and temperature.  By analyzing the sound of cricket chirps outside his home, he observed a correlation between temperature and the number of chirps per minute.  His work, titled “The Cricket as a Thermometer” was published in 1897.  The formula he used to relate the number of cricket chirps to temperature is known as Dolbear’s Law.

It is assumed that the crickets that Dolbear studied were snowy tree crickets. Throughout the years, follow up studies have been done to come up with slight variations of Dolbear’s Law based on different species of crickets and katydids.

Does it Work?  Try it Yourself!

This is a fun experiment you or your kids can try, based on one I found on Science Buddies.

All you’ll need is a stopwatch and a thermometer (the ones on your phone will do), and something to calculate your results.  You will also need access to crickets. While it is possible to buy crickets (often from pet or bait stores), this experiment can easily be done with the crickets found in your yard.  According to Science Buddies, the best results are obtained when this experiment is done on a day when the temperature is between 55 and 100 degrees Fahrenheit. Evening is often the best time to hear crickets chirp.

When you’re ready, focus in on the sound of a single chirping cricket.  Start your stopwatch and count how many chirps you hear in 14 seconds, then add 40 to that number.  This should give you the approximate temperature in Fahrenheit. Compare this temperature with the temperature indicated by your thermometer.  How close are the two temperatures? Are they within 5 degrees of each other?

If you don’t want to do the math yourself, there is even an online program that will do the work for you. The National Weather Service has a Cricket Chirp Converter which can be found here.

There are many variations that you or your children can do to take this experiment further:

• Try this experiment again, but this time count how many chirps you hear in 8 seconds.  Add 5 to that number to get the approximate temperature in Celsius. Which method got a result closest to the actual temperature, determining the temperature in Celsius or Fahrenheit?
• Perform this experiment at different times of the day and at different temperatures.
• Do different types of crickets make better thermometers?  The most common cricket in North America is the field cricket, but there are other native species as well (including the snowy tree cricket).  Design an experiment to allow you to determine if one species is a more accurate thermometer than others.

The story of Amos Dolbear and his crickets is a great example of the scientific method at work.  He made an observation, formulated a hypothesis, and conducted research to satisfy his curiosity. It is also an amazing example of the order and wonder that simultaneously exist in nature.

I hope you’ll take the time to try this experiment out for yourself. It’s a great way to get outside and explore the world around you!

Further Information

How to Tell the Temperature Using Crickets

Create Your Own Cricket Radio: Listen to the sounds of different species of crickets chirping.

Listen to Snowy Tree Crickets Chirping at Different Temperatures: Hear for yourself the difference that temperature has on the rate of chirping

The Old Farmer’s Almanac: Predict Temperature with Cricket Chirps: For years, The Old Farmer’s Almanac has listed Dolbear’s Law as a way to predict the outside temperature.

The Old Farmer’s Almanac: Pet Crickets and Cricket Facts: Learn interesting facts about crickets.

You Can Tell the Temperature From Cricket Chirps, Thanks to Dolbear’s Law: Read about what else Amos Dolbear is known for (and what he isn’t).