Last week a friend inquired about all of the racket created by unseen insects as scorching days melted into somewhat less scorching nights here in the DMV. Near sunset as we enter the twilight zone, shrill daytime calls of several species of annual, a.k.a dog-day, cicadas are replaced by the courtship serenades of hopeful dusk-calling male cicadas and male katydids. Specific frequencies, amplitudes, and tonal patterns are used not only for species recognition, but also by females of each species to decide who will be the father of their nymphs. The winners of the entomological version of ‘The Voice’ win the right to mate and thereby move on to the finals evolutionarily, so to speak. Cicadas produce sound by vibrating a membranous, drumhead-like organ on the sides of their abdomen called a tymbal. The enlarged and mostly hollow abdomen of the cicada acts as an amplification chamber producing vibrations of 100 decibels, one of the loudest sounds in the animal world.
Watch as an annual cicada scales a tree before taking flight to the canopy. The abdomen of a daytime-singing cicada vibrates as he woos his mate. Leaf-mimicking angle-wing katydids are common in our area. Grooming appears to be an important part of the daily routine. To hear the gentle call of the greater angle-wing katydid, please click on this link. http://songsofinsects.com/katydids/greater-anglewing
Katydids use a very different anatomical mechanism to create sound. The katydid’s remarkable musical anatomy includes a forewing with a series of teeth called the file and an opposing forewing with a scraper. When the file moves across the scraper, vibrations reverberate across the wing – the song of the katydid. The common true katydid, Pterophylla camellifolia, creates an amplification chamber by bowing its forewings to help resonate its call. The result is one of the loudest and most easily recognized of all katydid songs.
So, if the guys are singing their hearts out, female cicadas and katydids must be able to hear their songs, right? Right! Both male and female cicadas have membranes called tympana on their abdomen that enable them to detect vibrations. The auditory organs or “ears” of katydids are located inside chambers of the front of their forelegs. How strange. As the dreadfully hot summer day transitions to evening, listen for the calls of the dusk singing cicada and enjoy his attempts to woo a mate in the treetops. And as twilight transitions to dark, when the songs of cicadas’ end, soon will begin the chorus of the katydids, serenades of six-legged summer romances.
“Songs of Insects” by Lang Elliott and Wil Hershberger, the wonderful Songs of Insects website, and “The mechanics of sound production in Panacanthus pallicornis (Orthoptera: Tettigoniidae: Conocephalinae): the stridulatory motor patterns” by Fernando Montealegre-Z and Andrew C. Mason were used as references for this episode. Special thanks to Jen Franciotti for providing the inspiration for this episode.
To hear the song of one of our local dusk singing cicadas, the Northern Dusk-singing Cicada, Megatibicen auletes, please click on the following link: http://songsofinsects.com/cicadas/northern-dusk-singing-cicada
To hear the song of one of our local nighttime chorusing katydids, the Common True Katydid, Pterophylla camellifolia, please click on the following link: http://songsofinsects.com/katydids/common-true-katydid