Cicadas, known for their periodic appearances and distinct songs, often raise questions about their eyesight. Can these creatures truly see, and how do they perceive their surroundings? This article explores the visual world of cicadas, detailing the specialized structures of their eyes and how they interpret light to navigate their environment.
The Unique Structure of Cicada Eyes
Cicadas possess a sophisticated visual system with two distinct types of eyes. They have a pair of large, prominent compound eyes located on the sides of their head, often bright red in periodical cicadas. These compound eyes are composed of thousands of individual units called ommatidia, each containing its own lens and light-sensitive cells. This arrangement provides cicadas with a wide field of vision, allowing them to detect movement across a broad area.
In addition to their compound eyes, cicadas also have three smaller, simple eyes known as ocelli, arranged in a triangular pattern on their forehead. These ocelli are specialized for detecting changes in light intensity, helping the cicada orient itself.
What Cicadas Perceive Visually
Cicada vision, while not as sharp or detailed as human vision, is highly adapted to their specific needs. Their compound eyes excel at detecting movement. They can also perceive certain colors, particularly within the blue-green and ultraviolet spectrum. This ability to see ultraviolet light is important for their interactions with plants and potentially for finding mates.
The cicada’s visual system is also sensitive to changes in light and dark. This sensitivity, aided by their ocelli, helps them respond to shifts in illumination. While they do not form sharp, detailed images, their visual acuity is estimated to be around 1-2 degrees, allowing them to discern general shapes and movements in their environment.
Vision’s Role in Cicada Life
Cicadas utilize their visual perception for various behaviors throughout their adult lives. Their vision assists in navigating their environment, helping them avoid obstacles during flight and locate suitable perching spots on trees. The ability to detect movement is particularly useful for identifying potential predators, such as birds, allowing them to react and escape.
Vision also plays a supplementary role in mate finding, even though sound is their primary communication method. Visual cues, such as contrasting body colors, may help males and females recognize and orient towards each other. These capabilities contribute to their survival and reproductive success during their brief above-ground adult stage.