The Common True Katydid

Here is an unseasonable gift, a little reminder of those hot months not so far behind us:  The summer sound of katydids, recorded in the yard of my friend Bill Braine’s home in Cornwall-on-Hudson, upriver about an hour from New York City.

It is always a pleasure to visit Bill and family.  Inevitably the conversation turns to the subject I would simply entitle “cool things in nature,” and Bill, possessing a curious and appreciative mind, is always willing to do a little exploring, even if within the confines of his own neighborhood.  That evening in August, after dinner and a few drinks, we ambled out to the great outdoors of Bill’s back yard, taking along a recorder and microphone to check out the action.  What we found, naturally, was katydids.  Listen …

These are two katydids.  Actually its hundreds of katydids, but in the foreground are two katydids, perched very near to one another in the same tree–which I thought was odd.  Katydids, I reasoned, surely must be similar to cicadas in that their call is used primarily to attract a female mate.  Why, then, would these two male katydids–in such competition–reside so close to one another?  Were they on the verge of combat?  In my quest for an answer, I did a little internet research and came upon Susan Villarreal of the Department of Entomology at Cornell University, to whom I sent this recording.

Susan, I must say, was fantastically generous with her response, telling me in great detail about nuances of the recording that had flown right over my head.  The two katydids, she explained, were of a species called the Common True Katydid, or Pterophylla camellifolia.  Judging by the name I wasn’t on to anything too out of the ordinary, and the call of this species is heard throughout much of the eastern United States.  Susan further explained that the two individuals were  “counter-calling,” that is, they were alternating their calls to enable each individual to distinguish his call from the other.  Katydids, I thus learned, cooperate.

A further bit of internet research led me to more interesting facts about the call of the Common True Katydid.  One excellent source of information was the remarkable SINA, or Singing Insects of North America, website (http://entnemdept.ufl.edu/walker/buzz/index.htm), a goldmine for those who have a casual interest in katydids and other such creatures.  Of the many characteristics of the Common True Katydids that are discussed on this informative and clearly-presented site, the one that caught my eye was observation that Common True Katydids display regional variation in their song.  More precisely, there are three distinct variations to the Common True Katydid’s call and these three distinct calls are linked to three specific population ranges.  If this was an old folk song we were discussing, I’d say that the regional variation was due to the way katydids of a certain region learned their song from their neighbors, but I don’t really know – do katydids learn their songs?  Or is their “melody” a manifestation of their physical characteristics?  I’m strongly inclined to believe the latter, but I don’t really know.  Likely these questions are answered in Entomology 101, but I never took the class  For now I’ll just enjoy the questions.

Another recording:  Down by the river there was a cargo train heading north on the tracks along the west bank of the Hudson.  Big echo blanketed the town.  In reference to all the hubbub, Bill remarked that he generally thought his neighborhood was a quiet place, but when listening through the headphones to the sounds around him–to the sounds of car doors slamming and train tracks, of distant music and katydids–he realized just how full of sound his environs really were, just how many things were happening around him.  Following is a bit of the train sound as recorded in Bill’s yard.

(Note:  Listening to the compressed file online made me realize that the train might not be coming through very clearly; I’ll probably reload this file, but meanwhile I wanted to get this post up)

He should be a tour guide, Bill.  To drive around with Bill is always a blast.  In every direction there are things to see … the crest of mighty Schunemunk Mountain, the rusty red iron of the Moodna Viaduct, the distant Fishkill Range, Sugar the mastodon on the SUNY Orange campus in Newburgh, his friend’s microhydro power system.  On this night there were spiders in his yard, micranthenas, as Bill explains on the following track, which I recorded just to get an example of my his enthusiasm for all things natural.

(Though we shudder in fright, they are harmless, and small, and really, three spiders is not so many.  Still, better not to walk blindly through the woods and end up with a face full of spiderweb)

Finally, here is a recording of me recording a bug, babbling all the while.

—-

Now, for a little bit more about the katydid recording:  Susan can hear and identify two more species in the above track!  As she explains, ” … one is a ticking noise, best heard ~9-10s and 26-35s during your recording. The other is a high pitched trilling which if fairly constant throughout the file.”  To read this sentence in Susan’s email was a humbling experience.  I, who so often patted myself on the back in praise of my excellent listening skills, learned in one fell swoop what it really meant to listen carefully–a very good thing to learn.  Susan, meanwhile, identified the two sound sources:  The first, the ticking noise, she reckoned to be that call of the Greater Anglewing Katydid, Microcentrum rhombifolium, which, according to Susan, is an attractive insect and a great mimicker of the green leaves of the trees it inhabits.  The second call, the high-pitched trilling, was that of a tree cricket.  Tree crickets, she explained, were difficult to identify.  Without the benefit of examining an actual specimen, entomologists may still be able to identify the species by noting the frequency and pulse rate of the trill.  Using a software called Raven, Susan was able to examine a visualization of the recording.  Raven (an “Interactive Sound Analysis” software developed by the Cornell Lab of Ornithology) allows users to view a recording as a spectrogram.  In this case, as a chart with a horizontal X axis representing the passing of time, and a vertical Y axis indicating sound frequency.  Susan was thus able to see–in the spectrogram of my recording–an intermittent signal located on the Y axis at approximately 10.5-11kHz and 14.5kHz.  These tones, Susan further explained, were harmonics of the related predominant or fundamental tone at roughly 3-3.5kHz.  Found in a recording such as mine, this pattern of frequencies is indicative–to a trained entomologist–of a tree cricket.  Furthermore, based on the geographical location of the recordings and the fact that the sound was non-continuous, Susan concluded that the call was likely produced by either a Two-Spotted Tree Cricket (Neoxabea bipunctata), or the Narrow-Winged Tree Cricket (Oecantus fasciatus).  Here is a screenshot of the Raven visualization of a section of my recording, sent to me by Susan (the upper half is the waveform, the lower half is the spectrogram; Susan has marked with a “1” the visualized tree cricket call):

two katydids

(Also note:  In the blue waveform in the upper half, the three lumps on the left (and the two on the right) is a very loud and clear katydid call).

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