Calculating the Temperature with Chirping Crickets

Each summer the children and my aunt were sent to live at our "Country House". It was really just a cottage with barely two bedrooms, no bathroom, and a really small kitchen. There was no television, just radio. We could of had a television there, but didn't. There wasn't even a phone and cell phones were not available in those days. We would sit outside at night a listen to the crickets, catch fireflies, and look for shooting stars. Many years later while studying biology in college I learned that you could calculate the temperature from the chirp rate of a cricket.

Insects may make sounds by moving a different body parts like the wings, abdomen and legs against other body parts. Crickets use their wings in a process called "stridulation" to make their chirp. This sound is produced as a form of communication. Many times such communication is to attract mates and usually it is the male that makes the sound to attract the female. Sometimes they make sounds when they are disturbed, afraid, or establishing a territory. There are distinctive chirps for different types of crickets and crickets do chirp faster as the temperature increases.

(Note: The tree frogs in the mountains of Puerto Rico chirp at different rates in relation to their altitude on the mountain. It was really great to have had a chance to hear this while on a biology field trip there while I was in college.)

You may have a difficult time making these calculations because crickets may not chirp below 55 degrees F. or above 100 degrees F, it may be difficult to distinguish one chirp from another, the rate of chirp can be affected by age and other factors, and if there are several crickets chirping it may be difficult to isolate just one cricket to count.

There are several formulas that can be used to calculate the temperature. Fro a typical field cricket the formula is T = N/4 + 40. (The graphic may help.) There are different formulas for a snowy tree cricket and a katydid. In any case you could probably find a sound byte on the internet of a cricket chirping and then experiment with making some 30 to 60 second segments of the chirps. You could then change the rate at which the chirps are played and finally play this to students and give them a chance to make the estimates of temperature.

The Chinese would put crickets into a small cage inside their homes and a lot of stories have been written about crickets. I would not want to put any animal into a cage in the classroom unless I was certain that I could care for it properly and certainly would not keep it beyond a day or two. Remember that they do get into the house and seem to survive for several days, but many homes are sprayed for bugs which can't be good for a cricket.

It would be great to try this with students! This is the type of lesson that could easily combine math, social studies, and science in a really great integrated lesson plan. Note: A student made the drawings about 30 years ago.