There are 2,400 species of crickets that make a chirping sound by rubbing a scraper on one forewing along a row of “teeth” on the opposite forewing. Because crickets are cold blooded, their activity and metabolism are governed by temperature – increasing with heat, decreasing with cold.
As a result, they rub their forewings faster in hot weather than cold.
The relationship between number of chirps and temperature is surprisingly exact.
To calculate the air temperature in degrees Fahrenheit (T) from the chirp of the snowy tree cricket (Oecanthus fultoni), which is common all over North America, count the number of chirps per minute (n), subtract 40, divide by 4 and add 50.
Thus the formula is T (temperature *f) = { ( n – 40) / 4 } + 40
(courtesy of “ Man Eating Bugs” )