See what’s happening on the grounds of the Ames Free Library or nearby areas with “A Glimpse of Nature.” Offered by Lorraine Rubinacci, the library's resident naturalist, this weekly photo blog is a gentle reminder to enjoy the wonders that surround us.
A Glimpse of Nature - "Night Music"
During the past month, a spectacular natural phenomenon has been taking place here in Southeastern Massachusetts. I speak of the late-summer chorus of singing insects. While this annual event is savored by many, its seeming familiarity may diminish the attention it deserves, so that we humans forget to listen . . . to really listen. Hopefully, last week’s audio clip reminded my readers to step into the world of nighttime sounds.
I’ve known for months that this would be an interesting topic, but hesitated because I lacked photos. Then, my colleague, Marion Wingfield, sent me this image from her home in North Easton. How could I resist?
Photographing these animals does pose some challenges. Like the creature above, many are well camouflaged, nocturnal, and prefer not to be seen (or eaten). Then again, it’s never easy to find a subject when you’re looking for it. For that reason and because I want to engage your other senses, this post will concentrate on sounds.
When I began recording in early August, I thought I knew what I was doing: the chirps are field crickets, the katydids speak their name, and snowy tree crickets provide the background. The reality is considerably more complex and wonderful and, to the non-specialist, daunting. The more I listened, the more confused I became. So I faced my ignorance, and “hit the books” only to discover scores of singing insects, many of which live in Massachusetts. I can’t offer you firm IDs; I am not a trained entomologist or even an accomplished amateur. Nevertheless, I know that a good educator guides, points in the right direction, offers resources, raises questions, and elicits wonder. So, let’s make a start.
The nighttime singers include two large groups that may broadly be labeled “crickets” and “katydids.” Grasshoppers (locusts) and cicadas dominate the daytime shift. In addition to the familiar field crickets, the cricket “group” includes tree and mole crickets which look very different from the idealized cricket shape. Similarly, katydids encompass many more species than the common true katydid; among them are the distinctive coneheads. A fine overview can be found on Songs of Insects, an award-winning website created by sound recordists, Lang Elliott and Wil Hershberger.
|Grasshopper: short antennae||Katydid: long antennae|
Male crickets and katydids call to attract mates who find them through these songs. The Orthoptera (the order to which crickets & katydids belong) produce sound through stridulation, the rubbing of one body part against another. In this case, parts of their wings are rubbed together: a “scraper” on the lower wing, and a “file” on the upper. Each species creates a distinctive song whose pattern and frequency can be discerned by its members. For humans, it is sometimes helpful to compare sound spectrograms which transform the songs into a visual format.
As a rule, crickets sing at a lower frequency and produce a more musical song. Chirps consist of individual notes or brief trills alternating with pauses. Chirp, pause. Chirp, pause. The fall field cricket is a chirper.
This individual is chirping during the day with a blue jay calling in the background. It will continue to chirp at night.
Other singers produce a trill, a rapid series of sounds without pause. This conehead, a type of katydid, generated a loud buzzy trill right outside my window. While several other species punctuate the recording, the trill is sustained throughout.
Conehead singing in the rain (yes, it is facing the ground)
Here’s a second example of a trill which lasts for a minute and a half. Imagine how much energy it requires to sustain that motion!
Many katydid songs consist of rattles, ticks, and noises that might be described as mechanical. Let’s begin with the common true katydid which repeats short, staccato phrases: katy did, she didn’t, she did, etc. Once again, several other insect species may be heard, but the common true katydid is in the foreground.
While recording the dominant voices of the evening, I kept getting distracted by others. One was a loud ticking from the top of a small tree. This short audio clip captures two ticking sequences. Greater angle-wing katydids produce ticking sounds but, of course, I saw nothing!
Another species made a sharp, “zit” sound. This would be typical of the oblong-winged katydid. Here’s a brief sample.
These songs are intended to be heard by other insects who listen for them with their legs -- yes, their legs. According to The Songs of Insects, “Crickets and katydids have tympana located on the front legs at the base of the tibia.” If you are skeptical or need to refresh your insect anatomy, the website includes a nice closeup photo of an insect's eardrums.
Under natural circumstances, a female would have little difficulty finding a singing male of her species, but human-generated noise pollution may be undermining this process. I am more sensitive to noise than most people, but my awareness of noise pollution skyrocketed while I was listening for and trying to record these insects. Every time I turned on a recorder, a car or truck or plane passed by -- everywhere and at every time of day. I began to wonder, “If I can’t hear them, can they hear each other?” Perhaps not, and that could have serious consequences to all the creatures who depend on cricket and katydid meals. The online magazine, Inverse.com, describes the impacts of noise on singing insects in this article. To avoid distracting ads, switch your device to reader view.
There is still time to listen to insect songs this season . . . but not for very long. Crickets and katydids seek mates when they reach maturity in the latter part of summer. Then they copulate, lay eggs, and die with the arrival of cold weather. For most species, the eggs hatch in spring, and the cycle begins anew. As autumn progresses, fewer species will be singing, and their songs will be less energetic.
These are cold-blooded animals whose metabolism reflects the ambient temperature. Given that crickets chirp faster at warmer temperatures, the rate of their chirps has been used as a rough thermometer. One formula to calculate this is to count the chirps of a snowy tree cricket for 13 seconds, and then add 40. This number should equal the air temperature in degrees Fahrenheit.
Here’s some practice in listening with attention. Play this audio clip while making a tick mark for every chirp. Do a tally and add 40 degrees.
The cricket thermometer clip was recorded at 10:59 on August 24. Click this Weather Underground history to find the temperature on that date and time. The data is from Logan Airport, the nearest station with recorded history. It’s usually a little cooler in the suburbs, but it was, indeed, a hot night!
Tree cricket on window screen
Additional sound recordings may be found at The Cornell Lab of Ornithology’s Macaulay Library. To access insect sounds, change the green bird tab to “all animals,” switch to grid view, and search a species name. Here, for example, are recordings of the fall field cricket.
iNaturalist page for sightings of “Grasshoppers, Crickets, and Katydids” observed in Massachusetts
For visual identification, the Picture Insect: Bug Identifier app might be helpful. There is an annual fee of $29.99.
At the Library
by Lang Elliott
*This item can be found in the Commonwealth Catalog
by John Capinera et al.
by Theresa Greenaway