As fall moves ever forward to winter, the choruses of late summer and fall wane. These diminutive singers are such an integral part of late summer that most people don't realize the tremendous variety of species composing this orchestra. A walk in the fields would be a great introduction to some of these musicians and just how varied and numerous they are. You can find a nice variety of species in the fields and woods along country roads or river valleys.
Short-winged meadow katydids are by far the most numerous and perhaps the hardest to hear. As their name implies they have very short wings and as such produce a high pitched song (ca. 15,000 Hz).
Round-tipped conehead katydids were much easier to hear but, much harder to find. Their habit of dropping head first into the base of the grass tufts can make them hard to approach. Using a bright flashlight you can get lucky and see a male singing from his hidden podium. Also abundant are the Woodland meadow katydids, a robust little songster that is easily approached and observed. A real hit would be a singing Broad-winged tree cricket that could be found fiddling away from the underside of a leaf.
As the evening darkens the Common true katydids, the familiar singers of August and September, will start to sing. If it is a cool evening a slower version of their song will be delivered, “katy-did, katy-didn't.” They may not be recognized at first until you consider that all of these musicians are poikilothermic. They are subject to the ambient temperature and their songs and activity level reflects that. In fact, the Snowy tree cricket is so linearly controlled by temperature that counting the number of chirps in 13 seconds and adding that number to 40 provides a close approximation of the ambient temperature in degrees Fahrenheit.
Perhaps the best looking member of the orchestra that could be found is the Black-legged meadow katydid. These red-eyed, turquoise-winged insects are just stunning. Oblong-winged katydids and Lesser angle-winged katydids should also be encountered after dark. Look for them singing from low vegetation or from the side of a tree. Look for darkened areas on the tegmina (forewings) as an indication of damage by a recent frost.
All of these singers are members of the order Orthoptera – straight-winged ones. The orthoptera sing by rubbing their forewings together. The front pair of wings are modified in the males for the production of sound. These thickened tegmina are set up so that there is a file of small teeth on the bottom side of the upper tegmina that rubs across a thickened ridge, the scraper, on the top of the lower tegmina. Rubbing the file over the scraper sets thinner areas of the tegmina into motion creating the sounds that we hear. The insect holds the tegmina at such an angle as to create a chamber that amplifies the sound produced thus making it easier to hear and allowing the sound to travel farther. Their ears are on their front legs and are usually seen as a darker or lighter area near the joint. This mechanism of singing has been around for at least 360 million years. It is just amazing to imagine Tyrannosaurus rex resting in the jungles of the Jurassic period listening to insect choruses that sounded very similar to what we hear today.
As winter chills the air and the last of these musicians goes silent, please reflect on this marvelous phenomenon - the Fiddlers of the Fields.
For more information on the Orthoptera see:
By Wil Hershberger 2005