Song Analysis

by Carl Strang

One of my goals this autumn was to begin sorting out the meadow dwelling tree crickets of the nigricornis species group at Mayslake Forest Preserve. In earlier posts I shared some photos that pointed to a mix of species, but now I have studied their songs, and the results prove to be complicated. One individual was straightforward. He was unique in having an abdomen that was black beneath.

I immobilized him briefly in the freezer for photos.

I immobilized him briefly in the freezer for photos.

His antennal spots clearly distinguished him as either a black-horned tree cricket or a Forbes’s tree cricket.

There was clear separation between the spots on the second antenna segment, and those spots were narrow.

There was clear separation between the spots on the second antenna segment, and those spots were narrow.

When I looked at my recording of his song in the Audacity sound analysis program (available as a free download), the pulse rate clearly was that of a black-horned tree cricket.

The program allows the pulse rate to be counted, in this instance the interval between the 6-second and 6.5-second point in the recording. The pulse rate of 36-37 per second at 65.5F is unambiguously that of a black-horned.

The program allows the pulse rate to be counted, in this instance the interval between the 6-second and 6.5-second point in the recording. The pulse rate of 36-37 per second at 65.5F is unambiguously that of a black-horned.

The other tree crickets were problematic. Here is the most ambiguous case. His antenna spots, along with his generally pale coloration, said he was a prairie tree cricket.

The spots on the second antenna segment were thick, and had a very narrow space between them.

The spots on the second antenna segment were thick, and had a very narrow space between them.

On the other hand, his song had a very rapid pulse rate.

A pulse rate of 48 at 68F is close to that of a Forbes’s tree cricket.

A pulse rate of 48 at 68F is close to that of a Forbes’s tree cricket.

All the other tree crickets I tested had songs most like Forbes’s, but only one had the antenna spots to match. The others either were closer to those of the prairie tree cricket, or were ambiguous. The literature I have seen cannot carry me any farther. My next step will be to look at nigricornis-group tree crickets at other sites in 2013, and hope for enlightenment.

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1 Comment

  1. knapperbill said,

    December 6, 2012 at 9:32 pm

    What an excellent use for Audacity! I’ve used this program for a few years in my job, but never thought of using it for nature! Fantastic!

    Bill


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