Cicadas wait for this exact moment each morning to sing

Cicadas are early risers. Their synchronized choruses often mark the start of a summer morning. But new research has revealed just how precisely they coordinate this ritual.

Scientists have found that cicadas begin singing not just around dawn – but exactly when the sun is 3.8 degrees below the horizon. This moment, called civil twilight, creates just the right light level to trigger their song.

Cicadas sing at early morning light

The study was conducted by researchers from India, the UK, and Israel. They recorded cicada sounds over several weeks near Bangalore, India.

The team analyzed the data using tools from physics. Their approach was similar to how phase transitions in materials are studied.

Study co-author Raymond Goldstein is a professor in the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge.

“We’ve long known that animals respond to sunrise and seasonal light changes. But this is the first time we’ve been able to quantify how precisely cicadas tune in to a very specific light intensity – and it’s astonishing,” noted Professor Goldstein.

Cicadas sing at the same light level

Cicadas don’t just start singing slowly. The full intensity of their chorus builds within 60 seconds. The midpoint of that rise occurs consistently at the same solar angle, no matter when sunrise actually happens.

The research showed that cicadas respond when light intensity hits a narrow range, varying by just 25 percent.

This means cicadas are not just reacting to vague brightness. They are tuned to a precise visual signal in their environment. Direct measurements placed this critical light intensity at about 4–6 lux. The timing remains stable even with minor shifts in temperature or humidity.

Light tells cicadas when to sing

To analyze cicada decision-making, the researchers used a signal-processing method. They calculated an “order parameter” based on the chorus sound’s amplitude over time. This parameter grew in a sigmoidal pattern, rising sharply during the transition from quiet to full chorus.

When the light levels crossed a specific threshold, the sound amplitude jumped rapidly. This suggested the presence of a narrow decision window.

The researchers described this transition using a susceptibility curve – a concept borrowed from thermodynamics. The peak in this curve indicated high sensitivity to small changes in light.

Cicadas listen to each other

This sharp transition could not be explained by individual reactions alone. The scientists proposed a group decision-making process. Cicadas rely not just on light, but also on the sounds of nearby insects. This idea mirrors how midge swarms or firefly groups coordinate.

To support this theory, the team built a statistical model inspired by magnetism. In this model, each cicada behaves like a “spin” influenced by both the external light field and the activity of others.

As light increases, individual cicadas become more likely to sing – especially when others already have.

Working together to sing better

The model showed that moderate levels of interaction between cicadas created the best match to real-world data. Too little interaction resulted in slow, disorganized responses. Too much created spontaneous singing unrelated to light levels.

When tuned just right, the group amplified weak signals and responded swiftly and accurately. This behavior mimics a type of “group intelligence.”

According to the model, the strength of this interaction determines how precisely the entire chorus reacts to dawn.

The science of decision making

This work ties insect choruses to broader theories of collective behavior. Similar dynamics appear in ant colonies choosing new homes, birds flocking, and even human financial decisions. Each system involves individuals with partial information, guided by shared cues and local signals.

By studying cicadas and their singing patterns, researchers now better understand how organisms balance personal perception and social feedback. As the Earth rotates and light levels change, these insects make fast, precise choices – together.

“Rakesh’s observations have paved the way to a quantitative understanding of this fascinating type of collective behavior,” said Professor Goldstein. “There’s still much to learn, but this study offers key insights into how groups make decisions based on shared environmental cues.”

The study is published in the journal Physical Review E.

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