Gadget 1

by Carl Strang

For the most part in this blog I am trying to model methods of inquiry that don’t rely on technology. Our human senses have their limitations, but we can gather enough information through them to answer a lot of questions about our surrounding wild world. Nevertheless, there are occasions when gadgets can help. Today I will feature one of those I have found useful in my field studies of singing insects: my soprano recorder.

Recorder b

I don’t have perfect pitch, but I have a reasonably good ear. I have found the recorder to be especially helpful as I tackle the problem of the arboreal tree crickets (outlined in my earlier post on one of them, the two-spotted tree cricket ). This season one of my goals has been to sort out the songs of the two-spotted, narrow-winged and Davis’s tree crickets. I was encouraged when I noticed that Elliott and Hershberger, in their recent book on singing insects, indicated that these three species should have distinct pitches in their songs. Highest should be the two-spotted, at 3.5 kHz (kilohertz, a quantitative sound frequency measurement), which translates to a pitch of A, the fourth A above middle C. In the middle should be the narrow-winged tree cricket, at 3 kHz or approximately F-sharp, the fourth F-sharp above middle C, 3 half-tones below the two-spotted. I noticed, incidentally, that the distinctive song* of the snowy tree cricket also is indicated to be at 3 kHz, and so I had hopes that this would provide a rough and ready field standard. The lowest of the arboreal tree crickets, according to Elliott and Hershberger, is the Davis’s tree cricket, at 2.5 kHz. This translates musically to the fourth E above middle C, distinctly lower than any of the others. So, recorder in hand, I set forth.

Snowy tree cricket 5b

Snowy Tree Cricket

Two caveats quickly became clear. First, the pitch of a given species is subject to change with environmental temperature, rising and falling as the temperature rises and falls. Second, I have to keep in mind that my own hearing may not well match the measuring devices used to provide the information in that book. In general all species sounded, to my ear, a good 3 tones lower than Elliott and Hershberger suggested.

I have found that to my ear, both two-spotted and narrow-winged tree crickets have songs distinctly higher pitched than that of the snowy tree cricket. At a given temperature, the two-spotted sings one-half to a full tone higher than does the narrow-winged. However, at a given general temperature, narrow-wings range over half a tone of pitch or more. Whether this is because the microclimate is different where individual crickets are singing, or whether this is something they are controlling, I cannot say. It means, though, that I have to rely as much or more on the temporal pattern of the song to distinguish these two species.

Narrow-winged Tree Cricket

Narrow-winged Tree Cricket

Narrow-wings sing with a steady pattern of trills and spaces, with trills of equal lengths and spaces of equal lengths, and the spaces are significant at a second or so duration. Two-spotteds sing at a little higher pitch on average, have trills of varying lengths including some often lasting well over 5 seconds, usually with at least some pauses that are very brief, as though catching a quick breath.

I recently heard, on my neighborhood block count, what I believe must have been a Davis’s tree cricket. The insect was high up in a tree. Its trills were variable but generally very long, with only occasional odd interruptions. Spaces were short. Significantly, the pitch was down at A-flat, low for the temperature, which was 70F. Based on my recorder tests, at that temperature I would expect snowy tree crickets to be singing at B or C, two-spotteds at the E above that, and narrow-wings at C to E. So, the recorder is a helpful tool, but in distinguishing the songs of these crickets I find that the pattern of their song is more reliable than the pitch.

*You know the song of the snowy tree cricket, even if you live outside its range. In the movies, whenever the director wants to convey a calm nighttime mood, there will be a snowy tree cricket in the sound track. The song is a pulsing tone, varying with the temperature so that if you count the notes in 15 seconds and add 40, you have the temperature in degrees Fahrenheit. Though the narrow-winged tree cricket’s song likewise is a regular pulse, the tones are on the order of 2 seconds’ duration with a 1-2-second space between. Unless the temperature is very cool, the snowy’s song is much faster.

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