Long ago, the story goes, a newlywed couple was found murdered in their beds. Although the crime was never solved, the primary suspect was the bride’s sister Katy. And to this day, so they say, Kate’s fate is debated by one of summer’s most famous singing insects:
“Katy did.”
“Katy didn’t.”
“Yes she did.”
“No she didn’t.”
Such is the human interpretation of the call of the northern true katydid, Pterophylla camellifolia, or, “that being which has wings like a camellia leaf.” In our area, they began their discussion a few weeks ago; the chatter will wage on, night after night, until the last of the bunch succumbs to autumn’s hard frosts.
Although we tend to think of katydids and their cousins, the grasshoppers and crickets, as singers, they technically are fiddlers. To make their loud sounds, male katydids draw the rough edge at the base of one forewing across the bumpy, ridged edge of the other forewing (not one leg against the other, as we tend to think). This scraper-and-file method of sound production, known as stridulation, seems to work well; the bursts of song are as loud, or louder, than an average motorcycle engine.
The reason for all the noise is simple. It’s mating season in KatydidLand. The strident, repetitive calls are the sounds of males calling for females, who listen for and then select the mate they deem fittest.
A human female in a similar situation might cup a hand against her ear to distinguish amongst the calls, but a female katydid can do no such thing. Aside from the obvious problem of lacking hands, katydids “listen” with sensory organs located not on their heads, but rather on their front legs, just below the knees.
Male katydids listen to other males and alternate their calling frequency, creating loud choruses of back-and-forth discourse. Females listen and make their choices accordingly.
You can listen in, too. Just head out to an area with mature trees, right around dusk. The rhythmic calling is impossible to miss. But don’t count on seeing the callers themselves. Katydids are creatures of the treetops. Leafy green in color, they’re also nearly perfectly camouflaged. You can try shining a light up into the branches; about one in a hundred times you might spot a katydid strolling along a limb or trunk. But more often than not, all you’ll accomplish is a silencing of the singers.
Lucky for us, though, katydids can be kind of clumsy. When bumped or jostled—something that can happen during a particularly “busy” night—or caught off guard by a puff of wind, katydids flap and flutter and try to stay up high, but instead usually end up on the ground. Their large wings, it seems, just aren’t meant for flight. Oblong in shape, the wings are cupped around the body, a feature that makes for great acoustics but lousy aerodynamics.
Look for true katydids in the daytime underneath the trees in which they call. They’re good-sized insects, about the size of a woman’s thumb, with grasshopper-style legs and antennae as long as their body. Females are all green; males have a brown patch known as the stridulatory field just behind the head.
If math is more your thing, head out at night, but bring a calculator instead of a flashlight. Just as with crickets, it’s possible to tell the temperature by counting the calls of the katydid. Solve the equation T=(C+161)/3, with T being the Temperature and C the number of calls per minute.
Math was far from the mind of a person who called our office a while back inquiring about a “loud sound coming from the ash tree” outside her house. The caller was a bit exasperated as she described how the sound began at around 8:30 and continued long into the night, keeping her son awake; she described the noise as mechanical and repetitive, a “crick-crick” and sometimes “creek-creek-creek.”
It didn’t take long to respond when she asked what kind of animal had made the sound. Thanks to her apt description, the answer was simple: Katy did.
Pam Otto is the manager of nature programs and interpretive services for the St. Charles Park District and can be reached at potto@stcparks.org or 630-513-4346.