Dolbear's law

Dolbear's law is an empirical relationship between air temperature and the chirp rate of certain crickets. It provides an approximate way to estimate temperature from timed chirps.

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Snowy tree cricket: A North American tree cricket whose chirp rate varies predictably with air temperature. Dolbear's best-known formula uses this species' chirps per minute.
Amos Dolbear: An American physicist and inventor who published a relationship between cricket chirps and temperature in 1897. His name became attached to the cricket-temperature rule.
Field biology: The study of organisms in their natural environments through direct observation and measurement. Researchers can use insect calls as a rough environmental measurement in the field.
Ectotherm: An animal whose body temperature depends largely on heat exchanged with its environment. Crickets' activity rates respond to external temperature because they are ectotherms.
Cricket chirp: A cricket's calling sound, usually produced by rubbing specialized forewings together. The law uses the repetition rate of this sound as its observable input.
The American Naturalist: A scientific journal established in 1867 that publishes research in natural history and ecology. Dolbear reported his observation there in 1897.
Temperature measurement: The determination of how hot or cold a body or environment is. Dolbear's law offers an indirect alternative to instrument-based air-temperature readings.
Thermal performance curve: A curve showing how an organism's performance changes across environmental temperatures. Chirping does not necessarily rise linearly across the full temperature range.
Arrhenius equation: An equation describing how reaction rates depend on absolute temperature. Like many biological rates, cricket calling accelerates as temperature rises.
Cricket thermometer: An informal method of estimating air temperature by timing an insect's calls. Dolbear's finding became a popular natural version of a thermometer.