Wild Ideas: The sound of katydids fills the night

Aug. 22, 2013
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I love to hear thine earnest voice,
Wherever thou art hid,
Thou testy little dogmatist,
Thou pretty Katydid.

— “To an Insect,” by Oliver Wendell Holmes (1831)

If it seems I’m obsessed with bugs, I am, but this is the time of year when bugs are out and about, and this seems to be a buggy summer. Some butterfly species are out in record number. And the constant, loud chorusing of the common true katydid seems to come from everywhere in the forest canopy on a warm night.

A large female oblong-winged katydid, in the bush katydid family, blends in well with the giant-sunflower leaves it’s on. Photos by Pam Owen.

A large female oblong-winged katydid, in the bush katydid family, blends in well with the giant-sunflower leaves it’s on. Photos by Pam Owen.

Pterophylla cellifolia, the common true katydid, is in the Tettigoniidae insect family, which also includes grasshoppers and crickets, and in the subfamily Pseudophyllinae, “true katydids.” Oliver Wendell Holmes must have been talking about this particular katydid, since its chanting of “katy” is quite dogmatic and among the loudest of our native katydids. When many common true katydids are chorusing together, they tend to form into two groups and one group’s song will serve as counterpoint to the other’s.

Sorting out these sounds of these singing insects can be a real challenge, as I’ve noted in other columns, and I often rely on the sound files collected by Lang Elliott and Wil Hershberger for their book and accompanying CD, “Songs of Insects” (songsofinsects.com). The authors also offer other information on singing insects, some of which is not easy to find elsewhere, including spectrograms (or sonograms) of their calls, which help narrow the search before going to the sound files.

The katydids’ sound comes from them rubbing their forewings together. Males bow them out slightly to create a resonance chamber that intensifies their calls. In “Nature in Miniature,” author Richard Headstrom describes how crickets make their sounds, saying that the veins on the wing covers have veins that form a “peculiar” scroll pattern that “serves as the framework for making a sounding board of the wing membrane by stretching it out like a drumhead.”

“At the base of the wing,” Headstrom continues, “is a heavy crossvein covered with transverse ridges, called a file, and on the inner edge of the same wing near the base, a hardened area known as a scraper. The cricket sounds his notes by drawing the scraper of the under wing cover against the file of the overlapping one. We can produce a similar sound by running a file along the edge of a tin can.”

A tiny bush katydid nymph (about a half inch long) is more colorful than it will be in its adult form.

A tiny bush katydid nymph (about a half inch long) is more colorful than it will be in its adult form.

Headstrom goes on to say that male katydids sing in much the same way, “although they are left-handed musicians, having a file on the left wing only.” Rising heat can raise the rate and pitch of the songs of katydids, which hear each other through organs on their front legs.

Although anyone growing up in Virginia is familiar with the sound of the common true katydid, seeing one is another matter, since it typically stays high in the trees, especially oaks. Ranging throughout the eastern United States, it’s large (about 2.5 inches) and has a rounded appearance.

One branch of the katydid family, the bush katydid, is not so hard to find since, as the family name implies, these katydids are more likely to be found on bushes and other low vegetation. One of these species has been accenting the loud nightly chorus of its cousins up here on the mountain with its intermittent, loud, rasping clicks just outside my bedroom window each night. Likely it is the female oblong-winged katydid (Pterophylla camellifolia) that has been hanging around on the giant sunflowers I planted there.

One day I was inspecting the sunflowers for bugs and was within inches of this katydid before I saw her, since her lovely bright-green coloring blended in so well with that of the sunflower leaf on which she was perched. I had a hard time identifying the species because most of the references only describe the males’ appearance, including their genitalia, which is one of the best ways to sort out species.

With the sun behind it, this female’s curved ovipositor, used to lay her eggs, can be seen clearly under her wings.

With the sun behind it, this female’s curved ovipositor, used to lay her eggs, can be seen clearly under her wings.

The male oblong-winged has a dark stridulatory field (the area on the back over the sound chamber), while the female is green all over, as the one I found was. Not all oblong-winged are bright green; although rare, a few come in pink and tan, and even fewer in dark tan or orange. This species is the largest in its genus, almost the size of the common true katydid.

While it’s hard to sort out the sounds of many katydids and their cousins, the intermittent, loud “zee-dikh!” distinguishes the oblong-winged, as Elliott and Hershenberger point out. I found an insect nymph I couldn’t identify in my garden; someone at BugGuide.net suggested it was a young bush katydid, but wasn’t sure which species. Perhaps it is among the next generation of oblong-winged.

While the sounds of katydids may seem annoying to some, it lulls me to sleep on summer nights. I dread the long winter nights, when these and other singing insects are silent.

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