by Linda Martinson
It is usually not very noisy in the forests and fields of Richland Ridge, but there is certainly a cacophonous insect chorus after dark in the late summer into the fall. What we hear when we turn everything off and listen is a mixture of at least a dozen insect sounds, most of them produced by male katydids, tree crickets, and long-horned grasshoppers with the common true katydid leading the chorus. They are singing for female attention and a chance to mate before they are killed by a frost.
Although not what we are hearing now, in late August, cicadas began the season of loud insect choruses during the hot afternoons of the dog days of summer in late July and August. Locally, they are called jar-fly, annual, or dog-day cicadas, and the lore is that when their song is heard, the first frost is about six weeks away. Their song sounds like a loud hum or whine, and large numbers of them can sing in synchrony, pulsing from soft to loud and then back to soft. They make this common droning sound of summer afternoons by vibrating membranes on their abdomen.
The insects we hear at night a little later in the summer are mostly male katydids, crickets, and long-horned grasshoppers, and they produce sounds by stridulation, i.e., by rubbing one body part against another. To sing, most of them raise their front wings and move them back and forth. The sharp edge of one wing (the scraper) rubs against the ridge (the file) of the other wing producing a chirp or trill that is amplified by the wing membranes, much like the resonating sound a violin makes when the bow is pulled across the strings.
Male crickets begin singing at dusk creating a series of clicking noises, which sound like a trill or a chirp, by dragging a small peg of one wing against the ridges of the other wing, like dragging your fingernail against the teeth of a comb. Tree crickets make short and uniformly spaced trills that can be heard from a distance all summer long. Their songs are described as mellow, melodic, pleasant, and “almost defining a summer night.”
Later, the final singers of the night, the long-horned grasshoppers and katydids, take over and sing loudly almost until morning. In most deciduous forests, it is the common true katydid that sings most often and the loudest. They are not commonly seen because they live high in tree tops, especially oaks. This katydid is large, green, and bulky and resembles a leaf. It has large forewings but cannot fly; when they fall out of the trees after a storm for example, they walk along the ground to find another tree to climb.
The male true katydid of North America sings in quick bursts of two, three, or four notes. The sound has a crisp and harsh tone similar to saying the word “zit” with a prolonged Z sound with an abrupt T sound. Try saying it quickly three to five times, and you will be mimicking the sound of the katydids in the southeast whose songs have 3 – 5 pulses delivered fairly rapidly making each song sound like a quick rattle. Northern true katydids sing songs with 2-3 harsh pulses at a more deliberate rate, and in the southwest true katydids sing slowly with only 1-2 pulses in each song.
True Katydids often form large synchronized choruses alternating their songs with a call-and-response rhythm between tree tops usually drowning out every other sound in the area. When there are a large number of males in one location, each one will join one or the other of two singing groups. In this complicated alternation and synchrony arrangement, each male katydid is alternating with the neighbor he hears best, while at the same time synchronizing with the other males also alternating with that neighbor. This results in a large and pulsating and compelling synchronization of sound that can be frightening to people who haven’t heard it before. For example, the early Pilgrims wrote accounts about the terrifying insect sounds they heard at night in the late summer.
When the night temperatures begin to drop, the insects sing more and more slowly and their songs sound more creaky and “groaning” until they stop completely by October. So for the next six weeks or so, you can enjoy these strangely comforting night sounds of the insect choruses, and then they will end. But if you miss their songs in the winter, you can listen online or order an MP3 download or CD featuring ten relaxing lullabies of late summer and autumn insect choruses at http://songsofinsects.com an excellent and informative website created by Will Hershberger. Also check out their ideas for capturing singing insects, and keeping them through the winter to listen their songs.
Note: In July 2015, Dr. David Horn, an Emeritus Professor from the Entomology Department of The Ohio State University, gave a moth identification class at Richland Ridge for the Blue Ridge Naturalist Network. While collecting moths here, there was a storm one night, and the next day Dave found a specimen of a common true katydid on the ground, so he took a detour during the moth ID class and explained why they are rarely seen but often heard. Dave contributed ideas for this article including the reference from the songsofinsects.com website.