Originally published at Women Not Dabbling by Gina
Autumn is my absolute favorite season. I like most of the others (even winter!), but fall in the Midwest ranks the highest in my heart. Years ago, I turned in my area’s distinct season changes for the sameness of the American desert southwest. Though I truly love the mountains and cacti of the Sonora desert, by the time I reached my second fall season, I was homesick for the smell of decaying leaves and the cool nighttime/warm daytime temperatures. I missed the flamboyant colors of the deciduous trees and the chirping of crickets in the darkening night.
The cricket chirp is basically a male love-song to the cricket ladies. The sound is created by rubbing their front wings together in a process called stridulation. Katydids, a close cousin, sing their own song. Both are temperature dependent, meaning as temperatures increase so does the chirping and as the air becomes cool, the song takes on a more slow melody.
In 1897, a Tufts College physics professor must have been bored enough to discover a fairly accurate range of temperatures could be calculated by listening to this love-song. A.E. Dolbear devised a formula called aptly enough Dolbear’s Law. It centered on the relationship between chirps and air temperature.
TF = 40 + N
N=Number of chirps in 14 seconds
Tc = 10 + (N-40/7)
When using the song of the snowy tree cricket, the formula is accurate to about 1 degree. Other formulas, since Dolbear’s time, have been devised for the other less accurate species. Around here, the field cricket is the most commonly heard cricket. Apparently their song is not as accurate because it can vary by age and breeding success of the singers. However, there is a field cricket formula:
TF = 50 + (N-40/4)
Katydids have their own formula as well:
TF = 60 + (N-19/3)
Ok, this is not foolproof science. There are a few problems with Dolbear’s Law. First, crickets will become sluggish once the temperatures drop below 55 degrees F. or above 100 degrees F rendering the formula useless. Second, some cricket species create more of a single “trill” sound instead of a single chirp. Third, as mentioned, crickets can vary their songs when elements such as hunger, mating success, competition from other males and age are present.
I can attest, however, if you suffer from insomnia, laying in the darkness, trying to count the number of times a cricket chirps in 14 seconds to check the temperature is definitely a good way to bring on sweet, sweet sleep!