For those of you living near a forest or park you may have noticed the crickets chirping a little louder than usual. A coincidence perhaps? Not at all. Crickets are known to chirp louder and more intensely in relation to the heat.
This relationship is called Dolbear's Law and was formulated by American physicist Amos Dolbear in 1897 and documented in his article "The Cricket as Thermometer". In his article he accurately calculates the degree of heat based on the number of chirps per minute.
Because insects are cold-blooded, they are constantly in tune with and taking the temperature of their surroundings and this results in the cricket's chirp rate being based on their metabolism. Basically the higher the temperature the more energy the cricket has for muscle contraction which increases the intensity of their chirping. They create their chirp by rubbing the serrated edge from the top of one wing against the bottom of the other and when doing so, they hold their wings up and open into a kind of acoustical sail sending their trills and chirps out into the night air.
Here's a short orchestra recorded this evening: