August 23, 2012 —
If you live near a hardwood, or deciduous, forest, you would have heard these by now; in fact, they may even be keeping you awake at night if you have a bedroom window open. The evening chorus is courtesy of the common true katydid (Pterophyla camellifolia).
True katydids are a key phenology species. Phenology is the study of timing of periodic events occurring in nature. I usually hear calls starting right around the last week in July to the first week in August; this year, I first heard katydid calls in Pike County around the second week in July.
Katydids call to attract females, and only the male will call. True katydids generate this sound by rubbing the base of both forewings together to generate a two- or three-syllable call. Usually the ageless argument, “Katy did — Katy didn’t” is two males interacting with each other. If two males get within a few feet of each other, one or both may start “aggressive calling” with calls of four or more syllables; one will usually find another spot on the tree. Like that of crickets, the cadence of katydid calls will slow with cooler temperatures.
A strange trait of this species is that individuals found in the southern U.S. have a significantly different sounding call. An example of this can be found at www.musicofnature.org/songsofinsects/iframes/truekatydid/popup_ptercame2...  .
The true katydid is not the only katydid in the region; there are several species of “false” katydids. Meadows and fields abound with such varieties as conehead katydids and meadow katydids. They prefer the tall grass meadow habitats and they all have distinct calls. The short-winged neadow katydid has one call variation that sounds very much like a grasshopper sparrow. All of the meadow species also start singing near the end of July at night, but many of these katydids can be heard during the day as well.