a step too far

July 12, 2007

metrioptera roeseli

It’s been a beautiful warm day today, well at least from this afternoon onwards, and as a result the insects are a plenty.  As the day heated up not only did the insects become to be more abundant, but the crickets and grasshoppers also increased the speed of their chirps.  This is because their song is affected by temperature: as temperature drops their chirps slow down, and at the other extreme, when it gets too hot they conserve their energy and stop singing.

In fact, it is actually possible to tell the temperature by counting the number of cricket chirps.  Simply count the number of chirps a cricket makes in just over eight seconds, add 4 to your result, and you have the temperature in degrees centigrade.  It was a physicist named Amos Dolbear who first came up with the formula at the turn of the 20th Century, in 1897, publishing it in a paper entitled, “The Cricket as Thermometer” and giving it the name of Dolbear’s law.

Not all species of cricket respond in the same way, however, and so if you want to try this at home, it is probably best to experiment with a thermometer first to gauge how your local crickets react to the the temperature.  Also, be aware that some crickets are more reliable than others as they inconveniently change their rate chirp depending on their mating status and also as they get older.

A variation of the formula would also work for ants footsteps, if it was possible to measure them as they also follow the Arrhenius equation closely, but that’s probably going too far!

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