Crickets (Gryllidae) are insects distantly related to grasshoppers, found all around the world from grassland, bushes, and forests to marshes, beaches, and caves, except at latitudes 55° or higher.
There are more than 900 species of crickets, the largest of which are the bull crickets, measuring 2 inches in length.
Crickets are mainly nocturnal, and are best known for the loud, persistent, chirping song of males trying to attract females, although some species are mute. Crickets chirp by rubbing together the tough, leathery covers of their front wings.
As explained by Scientific American:
[T]here’s a special structure on the tops of their wings, called a scraper. When they want to make their sound, they raise their wings to a 45-degree angle and draw the scraper of one wing across wrinkles on the underside of the other wing, called a file. It’s somewhat like running your finger along the teeth of a comb.
But did you know that we can actually tell what temperature it is from their chirps? The chirps of these tiny creatures can be used as a kind of thermometer!
Crickets, like all living things, have many chemical reactions going on inside their bodies, such as reactions that allow muscles to contract to produce chirping. Crickets, like all insects, are cold-blooded and take on the temperature of their surroundings…. As the temperature rises, it becomes easier to reach a certain activation energy, thereby allowing chemical reactions, such as the ones that allow a cricket to chirp, to occur more rapidly. Conversely, as the temperature falls, the reaction rates slow, causing the chirping to diminish along with it.
As far back as the late 1800s there have been articles published noting that a cricket’s chirp rate (or number of chirps per second that it makes) changes consistently based on the outdoor temperature.
Scientific American has instructions on how we can test this remarkable phenomenon:
- Materials needed: an outdoor thermometer; stopwatch; piece of scratch paper; a pen; and most importantly, access to crickets or purchase your own cricket.
- On an evening when the outdoor temperature is between 55 and 100 degrees Fahrenheit (12 and 38 degrees Celsius), set up the thermometer to measure the outdoor temperature in the area where crickets are. Make sure you hear some chirping. Alternatively, if you purchase crickets, set them outside in a cage in the shade that allows the outside air to easily reach them. Wait until you hear chirping.
- Pick out the chirping sound of a single cricket. Count how many chirps the cricket makes in 14 seconds. Write this number down.
- Do this two more times, counting how many chirps the cricket makes in two more 14-second intervals. Write these numbers down.
- Average the number of chirps in the 14-second intervals.
- Add 40 to the average number of chirps. It should give you the approximate temperature in degrees F.
- Check the temperature on the outdoor thermometer. How close is the temperature based on the cricket chirps to the thermometer reading?
To determine the temperature in degrees C:
- Count the number of chirps in 25 seconds.
- Divide this number by 3 and then add 4.
Using the above equations, the numbers you get are usually within about 5 degrees F of the temperature measured using the outdoor thermometer. If the cricket’s chirps say it’s colder than the thermometer read, this can be because the cricket was farther away from a warm building than the thermometer was, and/or because the cricket was closer to the cold soil. The snowy tree cricket is frequently cited as the most accurate at predicting temperature.