Fall is in the air

Katydids: The Last of Summer's Songsters

Fall is in the air. Wood smoke is curling up from the cabin’s chimney and the hickory that overhangs it is beginning to hint at the yellow that will soon rival the sun’s brilliance. The brown leaves scatter ahead of me as I crunch along the trail. On a day so clear that the sky is the uninterrupted azure of the sea, a black dot circles and turns southwest—either a migrating monarch or hawk hurrying to a warmer clime. The chipmunks even seem to scurry a little faster as they carry leaves and sunflower seeds to their nests.

All these observations suggest that summer is passing into fall, but it is the sound I hear one evening that truly convinces me. The katydids are slowing down.

Katydids are leaf-shaped grasshoppers. Uniformly green, about 2 inches in body length but with legs and antennae that are longer than the body, these emerald tear drops are beautifully camouflaged against the lime-green leaves of trees. The wing coverings are even spider-webbed with veins like those of leaves. They are rarely seen on the forest floor until fall, when they fall or fly from the treetops down to earth. They eat leaves and are one of the insects responsible for adding so many holes to the leaves of tulip trees that they look like Swiss cheese.

Katydids, like other cold-blooded insects, are affected by temperature. The colder it gets, the slower they move. Katydids make their famous “katy-did” call by rubbing their wings together. As the nights get cooler, the orchestra begins earlier and moves more slowly, from “katy-did-katy-did-katy-did” to “kayy-teee-did.”

Insects are so dissimilar to us mammals that we often have difficulty understanding them. Empathy for most insects is a challenge, but, like us, they are organisms adapted to their environment and have found ways to prosper. Since we are so distantly related to them, however, those adaptations can be quite different from our own. Take ears, for instance. The most basic structure in their ear and ours is the same—a tympanic membrane stretched tightly over the rim of an opening. (Incidentally, the tympani in an orchestra are the drums.) Their eardrums, however, and those of most other crickets and grasshoppers, are placed on their front legs instead of the sides of their heads. Insects are, after all, known for their many specialized legs!

One species of cricket, called the snowy tree cricket, is so attuned to temperature that the frequency of its call can be used to estimate the temperature within a degree or two. Katydids aren’t as accurate, but you can try adding 161 to the number of calls per minute, then dividing the result by 3 to get an estimate of the temperature in degrees Fahrenheit. Remember that you’ll only get an estimate!

Female Katydid (note scythe-shaped ovipositor)

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