Night Buzzers

Have you had your windows open in the evenings and heard the night noises?  Chirping, trilling, and buzzing sounds all provide a delightful background to quiet evenings in autumn.  The sounds come from a variety of insect species including crickets, katydids, and cicadas.

One method insects use to produce these unique songs is called stridulation.  Crickets have a scraper on the edge of one wing and a serrated ridge on the opposite wing.  When the scraper is moved across the ridge, a chirp can be heard.  Crickets may move their wings slowly creating a continuous chirping sound, or more rapidly, creating a smoother and higher-pitched trilling.  Katydid also uses this method with a row of stridulatory veins on the undersides of both forewings.  Each row has small teeth-like protrusions.  When the wings are rubbed together and the teeth slide over each other, a similar clicking sound can be heard.

Cicadas use another method involving an organ called a tymbal to creating their unique night buzzing.  The tymbal, located on their abdomen, is a pair of ribbed membranes that can be flexed against each other.  When they are engaged, a ticking sound is created.  When moved rapidly, the continual ticking is heard as a buzzing sound.  Behind the tymbal, a hollow chamber in the body is used to amplify the sounds.

Stridulation in cricket species can only be performed by male crickets.  Each species has a unique set of sounds, and there are songs for attracting a mate over a distance as well as a courtship song when she draws near.  He may also use a warning sound to ward off any other males infringing on his territory.  Tree crickets have long, skinny bodies, live in trees, are nocturnal, and their color is adapted to their habitat.  In order to project their call further, they may pull a leaf together around themselves to amplify the sound.

Katydids are nocturnal, from 1/2 to 5 inches in length with a leaf-like appearance that provides excellent camouflage for this tree-dweller.  There are over 8000 species in the United States, each with its own distinctive song.  Katydids can create everything from soft to loud, harsh sounds.  Both sexes can create sound and it is used for many forms of communication.  There are songs to attract a mate, songs to warn off potential competitors, songs that provide information about a potential mate, and songs that warn the nearby  community of danger.

Cicadas create a buzzing sound that can be heard across short distances.  Much of the buzzing we attribute to them comes from several individuals together in one area.  Songs are unique among each species and used similarly for attracting mates and establishing territory.  In addition, a large group of cicadas will use buzzing to drive away potential insect predators who are intimidated by louder sounds including robber flies, mantises, and spiders.

Maybe you will take a stroll this evening, or open your windows for some nighttime air.  Be sure to listen for the music in the background of the evening.