I went out to stretch my scales in the Pollinator Garden the other day and got startled by a very loud buzzing sound! I tried to hide in my coworkers’ pockets, but they told me the buzz was just the sound of an annual cicada singing in the lilac bush and that it is a sign of summer.
Interestingly, only the males make those loud sounds! They have an organ in their abdomens called a tymbal, which they expand and contract to make a buzzing noise. The females are attracted to the buzz and respond back to the male by making softer clicking sound.
Unlike periodical cicadas that only emerge every 17 years, annual cicadas do not have a synchronous life cycle. This means that some adults are seen every year, rather than all of the adults emerging at once in the same region. The average lifespan of an annual cicada is between 2 and 5 years, so not all of the nymphs are emerging every year!
Females lay their eggs inside thin twigs. After the eggs hatch, the nymphs drop to the ground and burrow into the soil to find tree roots. They eat by using piercing mouthparts to suck sap from the roots. As the nymphs move between trees, their tunnels aerate the soil, which in turn helps improve the movement of water and nutrients and encourages healthy forests.
When it is time to complete metamorphosis, the nymphs emerge from the soil and find a tree trunk, rock, or other place to climb upward. Once away from the soil they shed their skin, leaving behind the brown hollow shells that are frequently seen in the park at this time of year! The newly-emerged adults cling to their shells as they pump fluids into their wings and wait for their exoskeletons to harden. The adults live for 5 to 6 more weeks, feeding on tender twigs and similar plant materials. During this time, the adults are a favorite food for birds, spiders, wasps, and other insect-eating animals!
I learned that there are over 3,000 species of annual cicada worldwide, and about 160 found in the United States. That’s a lot of buzzing! Luckily, my coworkers said that only 3 of those species are common in the park – the Northern Dog-day Cicada, the Northern Dusk-singing Cicada, and the Morning Cicada (also known as the Swamp Cicada). Each species has its own song and time of day that it sings!
The Northern Dog-day Cicada sings a high pitched 15-second long drone that starts soft, gets louder, and then fades off at the end. It is most commonly heard in July and August – the “Dog Days” of summer when Sirius (the Dog Star) is visible at sunrise. The Northern Dusk-singing Cicada emerges around the same time as the Dog-Day Cicada but prefers to sing for 30 minutes around sunset. Its song is a lower-pitched, pulsating drone that stops abruptly after 15 to 20 seconds. Meanwhile, the Morning Cicada sings a shorter song which starts as a soft buzz that rises as a pulsating drone before getting quieter and coming to a sudden stop. As their name suggests, they can mostly be heard singing between early morning and noon.
I would love to hear which cicadas you are finding in the park! Stop by the Visitor Center to let me know – my tank is in the front room.
Your friendly neighborhood corn snake,