Dolbear's Law
Encyclopedia
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
and the rate at which snowy tree crickets (Oecanthus fultoni, a tree cricket
Tree cricket
Tree crickets are insects of order Orthoptera. These crickets are in the subfamily Oecanthinae of the family Gryllidae.They live in trees and shrubs, for which they are well camouflaged. Like other species of cricket they produce their calling song by rubbing the ridges of their wings together...
) chirp. It was formulated by Amos Dolbear
Amos Dolbear
Amos Emerson Dolbear was an American physicist and inventor. His patents interfered with Guglielmo Marconi's planned activities in the U.S. Dolbear researched electrical spark conversion into sound waves and electrical impulses. He was a professor at University of Kentucky in Lexington from 1868...
and published in 1897 in an article called The Cricket as a Thermometer.
The chirping of the more common field cricket
Field cricket
Field crickets are insects of order Orthoptera. These crickets are in subfamily Gryllinae of family Gryllidae.They hatch in spring, and the young crickets eat and grow rapidly. They shed their skin eight or more times before they become adults.Field crickets eat a broad range of feeds: seeds,...
s is not as reliably correlated to temperature — their chirping rate varies depending on other factors such as age and mating success. In many cases, though, the Dolbear's formula is a close enough approximation for field crickets, too.
Equations
Dolbear expressed the relationship as the following formula which provides a way to estimate the temperature TF in degrees Fahrenheit from the number of chirps per minute N:
This formula is accurate to within a degree or so when applied to the chirping of the field cricket
Field cricket
Field crickets are insects of order Orthoptera. These crickets are in subfamily Gryllinae of family Gryllidae.They hatch in spring, and the young crickets eat and grow rapidly. They shed their skin eight or more times before they become adults.Field crickets eat a broad range of feeds: seeds,...
.
Counting can be sped up by simplifying the formula and counting the number of chirps produced in 15 seconds (
):
Reformulated to give the temperature in degrees Celsius(°C), it is:
A shortcut method for degrees Celsius is to count the number of chirps in 8 seconds (
) and add 5 (This is fairly accurate between 5 and 30°C):
The above formulae are expressed in terms of integers to make them easier to remember — they are not intended to be exact.