Insect Songs: Dog-Day Cicada - Neotibicen canicularis & Black-Legged Meadow Katydid - Orchelimum nigripes
In today's exploration of insects and their songs, we 2 familiar species today that are quite prevalent in Ontario's summer months. Previously, we had a look at the chirping of a Fall Field Cricket and how his chirp is actually composed of individual clicks. Today, we're going to begin by first examining the tree-dwelling shriekers that seem to grow even louder when heat increases. Just as with Crickets and other Orthopterans, the large-bodied Cicadas only sing if they are male. To produce their sound, they rapidly expand and contract a membrane behind their thorax called a tymbal. Knowing this information, you can actually identify males and female by looking for the tymbals, which (in this specie) is located underneath the wing. Be very gentle when handling a Cicada in order to see this membrane. If it screeches in response, it's definitely a male! To clarify with certainty, unlike Orthopterous insects, Cicadas do not use stridulation to produce their mating call, as that process describes insects rubbing certain body parts together to produce sound. Vibrating a membrane doesn't match the description. If anything, it's more like flexing a muscle and allowing the hollow-filled body to amplify the sound so that all can hear it.
Pictured below is a typical example of how a Cicada song normally appears in audio form. It is a distinct, clear sound. Headphone warning: a Cicada's shriek can be very shrill and grating, even if the amplitude has been gently reduced.
As mentioned in this blog's 100th post, the Cicada's song appears continuous because of the tremendously rapid expansion and contraction of this membrane. The muscles controlling the membrane are so powerful that the tymbal can vibrate several hundred times per second! The faster the vibration builds (for this specie), the higher the pitch of the song becomes. That said, just as a Cricket's chirp can be isolated to clicks, a Cicada's song can be slowed down to hear the individual pulses. After slowing the screeching down by several hundred times, this is the result:
On the other side of the summer of insects, most male Katydids generate their mating calls using wing-to-wing stridulation. There are exceptions of course (such as the Drumming Katydid), but today's specie has a loud method of communication! Like its Cricket friends, the loud, continuous sound is many clicks in rapid-succession. In fact, you can actually hear the beginnings of the clicks at the start of the song before the wings suddenly accelerate and song the clicking into overdrive! Considering the role flight muscles play in controlling the wings and their noises, it's no surprise how the song can turn loud very suddenly. It's possible that the song can only be sustained in short bursts to prevent muscle damage or heat buildup, but it also may be a precaution to exposing oneself to a predator with strong hearing. The sound is prominent and alluring, for both mate and hunter alike. Pictured below is a typical example of the Black-Legged Meadow Katydid's song (headphone warning):
Do note, that while this is louder compared to the Cicada song, I was much closer to the source. If I was next to a singing Cicada, that too would have been an incredible amount of sound volume! Nevertheless, when this Katydid's song is slowed down, the individual clicks become more prominent. Looking at it immediately after slowing the tempo down a few hundred times, a quick burst of less that one second becomes nearly 45 seconds worth of clicks! To showcase this, I've included a "portal" that offers a zoomed in look at the slowed song. Each spike in amplitude is a click of the wing-scraping. Even at reduced speed, you can hear the gradual acceleration of the clicking as the song goes on (headphone warning):
Pictures were taken on August 24, 2019 (Dog-Day Cicada) with a Samsung Galaxy S4 and on September 5, 2021 (Black-Legged Meadow Katydid) with a Google Pixel 4. Audio amplitude graphs were created using Audacity and samples from the following blog videos:
Black Legged Meadow Katydid | Dog-day Cicada