As autumn approaches, take advantage of the balmy evenings to measure the atmospheric temperature from cricket song. Count the number of chirps a minute, add 50 and divide by 9 to get the ambient temperature in degrees celsius. Tests with the Snowy Tree Cricket Oecanthus fultoni suggest that the chirp rate is regulated by the insect's metabolism, which is related to its absolute temperature by the Arrhenius equation, deduced in 1889 by the Swedish chemist of the same name. New Scientist