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The always-entertaining Robert Krulwich had a fun segment on ABC World News Monday night about using cricket chirps to calculate temperature. Apparently, as male crickets heat up, they chirp more rapidly. By counting the chirps, especially of one species, the Snowy Tree Cricket (Oecanthus fultoni), you can get a fairly accurate temperature. Here’s how:

  • Find yourself a cricket (a chirping one will be a male. A Snowy Tree Cricket (seen here) is the most accurate, but in a pinch, any cricket will do)
  • Count the chirps in a 14-second interval
  • Add “38” to the total
  • That’s the current temperature, in Fahrenheit

The discoverer of this phenomenon, known as Dolbear’s Law, was American physicist and inventor Amos Dolbear, in 1897.

The Krulwich piece name-checked entomologist and cricket expert Dr. Thomas Walker. You can find out more about him, crickets, and hear sound files at his website: Singing Insects of North America. Here’s a direct link to the field recording of the Snowy Tree Cricket.

This temperature hack only works above 45-degrees Fahrenheit. Below that, crickets get sluggish. If they get over-heated (above 90 F), crickets start chirping a lot less to conserve energy (don’t you?). You can also subtract 38 from the current thermometer temperature to get it in cricket. As I type this, it’s an unseasonable 42-chirps here in our nation’s capitol.