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.

## 6 thoughts on “HOW TO – Tell Temperature with Crickets”

1. garethb2 says:

BTW: I used the 14-seconds + 38 as Krulwich did in the ABC News piece. Several different sites have different formula. The actual Dolbear’s Law (simplified) is 15-seconds + 40. Since Krulwich talks to an entomologist in the piece, and it sounds like he consulted with Dr. Walker, I assume the current formula is 14/38.

2. jschrier says:

Actually, the chirping follows the Arrhenius rate equation, which is only approximately linear in the 45-90 degree F range.

This was discussed by K. J. Laidler, J. Chem. Educ 49, 343 (1972). [Finally, all those days of wasting time in grad school by reading back issues of journals is paying off!] There is also a discussion online.

If I remember the Laidler article correctly: (1) firefly blinking rate, and (2) human perception of time (without counting), can also be fitted with physically reasonable parameters.

3. garethb2 says:

Thanks for those links. I had a bit of a time following the Wikipedia entry, but that second link makes it much clearer. Folks might want to read these in reverse order. The K. J. Laidler piece is written for more of a lay audience (chem students).