Now that summer is winding down and temperatures have begun to moderate, it’s a joy to sleep with a cool, gentle breeze wafting through open windows. The sounds of nature make a perfect lullaby.
The voices of owls and frogs subside in September, allowing insect sounds to dominate summer nights. From late July until fall’s first hard frost, the sounds of insects are difficult to miss.
The best time to hear late summer insects is after dark, when orthopterans monopolize the nightly concert. Members of the insect order Orthoptera include the insects commonly known as crickets and grasshoppers.
Most people know the familiar black field cricket that lives in backyards everywhere. And I’m sure I’m not the only one who has spent sleepless hours searching for a rogue field cricket that turned the house into its own personal concert hall.
From a distance, the field cricket’s high-pitched trill is soothing and pastoral. But in the bedroom at 2 a.m. even a solitary cricket can almost drive a person mad.
Another widely recognized sound of late summer is the song of the katydid. Katydids are large green grasshoppers. They are often attracted to outdoor porch lights.
Their green textured outer wings resemble leaves and provide almost perfect camouflage for hiding in vegetation during daylight hours. Katydids also have extremely long antennae that arch back over the length of the body.
But the best way to recognize a katydid at night is by ear. Like birds, each species produces its own unique sound.
Males sing from early evening well into the night. The sound is harsh and burry — something like “Ch-ch” or “Ch-ch-ch” or “ch-ch-ch-ch.”
The phrases are repeated about once a second, and the rhythm suggests the insect’s name: Ka-ty, ka-ty-did or kay-ty-did-did. Occasionally, several individuals sing in unison to form a genuine chorus. I’ve often listened as two individuals dueted matching songs until they finally sang as one.
The singer of another familiar summer nocturne remains a mystery to most people. Snowy tree crickets generate a seemingly endless series of high-pitched melodic chirps that almost define a late summer night.
This is the insect sometimes called the “thermometer cricket” – count the number of chirps in 13 seconds, add 40 and you have a rough estimate of air temperature (°F). Though not precise, these estimates are usually in the ballpark and are based on the observation that snowy tree crickets sing faster when temperatures are warmer.
Though often heard and recognized, snowy tree crickets are almost impossible to find without a diligent search. During the day, they feed and rest amidst the foliage of trees and shrubs. Thanks to their small size and cryptic pale green color, they blend in with their surroundings.
At night, their song has a ventriloquistic effect. Shine a light where you’re certain the tree cricket must be, and sure enough, it’s not. It takes good eyes, patience, and a little luck to find a singing tree cricket.
Katydids, crickets, and grasshoppers produce the sounds we hear by a mechanical process called stridulation – they rub one body part against another. In the cases of the species I’ve described, the body parts in question are the front wings.
To “sing,” they elevate their front wings and move them back and forth. Where the wings overlap, a sharp edge (the scraper) on one wing rubs against a file-like ridge (the file) on the other. Membranes on the wing act as a sounding board to amplify the sound. The process is not unlike the notes that resonates from the body of a violin when the bow is pulled across the strings.
For more information and recordings of the songs of these late summer singers, refer to The Songs of Insects (complete with a CD) by Lang Elliott and Wil Hershberger (2007, Houghton Mifflin Harcourt). It covers dozens of species of crickets, katydids, and grasshoppers and is lavishly illustrated with beautiful color photos. Though out of print, used copies can be found on amazon.com for less than $10.