Naturespeak A naturalist's view of the world

August 13, 2008

Crickemometer

Filed under: Uncategorized — wykes @ 6:43 pm

   Let it here be recorded that at exactly 5:25 am on the morning of August 13, 2008, the temperature in Monroe, MI was exactly 68 degrees F.  This alone is not an earth-shattering revelation, but what if I tell you that this fact was determined with a watch and a pair of eardrums?  Now, perhaps, the thing becomes slightly more than a madman’s rant, yes? Throw in a dead guy and a chorus line of crickets and you have either the makings of a good joke or good science. Fortunately, in this case, we have good science and no bar or saloon references.

  Around about this time of year, a half-inch critter called the Snowy Tree Cricket begins to make itself heard. These pale elongated insects sport a pair of incredibly long antennae and are arboreal in habit. Individually, they have nothing special to offer – at least visually (see above a photo from a Univ. of Florida site).  These un-assuming little beasts spend most of their time secreted away in shrubby cover and only rarely reveal themselves. But, like most members of their type, they are singers that boldly announce themselves through evening song.

  It took a scientist by the name of Amos Dolbear to figure out that the song of the Snowy Tree Cricket (Oecanthus fultoni) contained a secret message.  Actually, I’m not sure that he was a scientist per se, but this is usually what you call dead people who make up formulas. In 1897, Mr. Dolbear came up with a mathematical method of correlating ambient temperature with the call rate of this cricket. While it had long been known that crickets in general “crick” faster on warm nights than cool ones, no one could come up with a simple way to calculate this effect. In other words, someone needed to figure out how a cricket could be used as a very precise thermometer.   

  Dolbear’s formula finally created just such a crickemometer out of the Snowy Tree Cricket. By counting the number of chirps in one minute then subtracting 40 from that number, dividing by 4 and adding 50 you end up with the absolute temperature in degrees Fahrenheit. This whole thing can be further simplified by counting the number of chirps in 15 seconds and adding 40 – in other words: T (temp.) = N (number of chirps per 15 sec.) + 40. Now, that’s do-able.

  The nice thing about Amos’s Tree Crickets is that all the individuals in one area call in unison. They synchronize their chirps so that the overall sound effect is like one call from one giant cricket rather than a hundred different calls from a hundred different individuals like most crickets. Listen carefully to this series of chirps (Snowy Tree Cricket Call) and you’ll note the soft pulsating rhythm of this species as I heard it at 5:25 am.  Start tapping your finger to the beat and count the beats in 15 seconds.  You’ll count about 28 chirps. Just add 40 and you have 68 degrees F.

  All of this cricking is performed by the males.  They rub a 35 tooth file across a rasp located on their inner wings (here’s a male in full performance- another great Univ. of Florida shot).  

  Apart from the mathematical precision of the tune, there is a comforting quality to this soft mantra. You’ve got a few months left to listen to these audible thermometers before they read 32 degrees F. sometime in October (at which point they are dead!).

1 Comment »

  1. Well I truly liked reading it. This post offered by you is very constructive for proper planning.

    Comment by Joseph Crutchfield — June 23, 2012 @ 2:16 am

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