Crickets are recognizable insects, known for the rhythmic chirping that often fills summer nights. Their presence is frequently noted around homes, especially near exterior light fixtures, leading to the common observation that they are attracted to light sources. This behavior is not a simple preference but a complex interaction between the insect’s evolved sensory systems and the modern environment. Understanding this phenomenon requires looking at the specific biology of the cricket and its ancestral navigational instincts.
The Cricket’s Relationship with Light
Most common species, such as the house cricket (Acheta domesticus), demonstrate a strong behavioral tendency to move toward a light source, a reaction known as positive phototaxis. This attraction is most pronounced during their active, nocturnal hours when they are foraging or seeking mates. Crickets frequently gather near exterior lights, indicating a deliberate movement toward the illumination. This behavior leads many pest control recommendations to suggest limiting outdoor lighting to reduce cricket presence.
The response is not universal across all cricket species. For example, the camel cricket (Ceuthophilus spp.) is repelled by light, exhibiting negative phototaxis and preferring dark, damp environments.
How Crickets Perceive Light
The ability of a cricket to detect and react to light is rooted in its specialized visual anatomy, which includes both large compound eyes and simple eyes called ocelli. The compound eyes allow the cricket to perceive a wide field of view and detect motion. Ocelli, located on the top of the head, are simpler structures primarily involved in detecting light intensity and maintaining flight stability.
The cricket’s visual pigments, or opsins, are highly tuned to specific wavelengths of light, which governs their attraction. Crickets possess visual pigments with peak sensitivities in the green, blue, and ultraviolet (UV) range. This spectral sensitivity means they are far more responsive to short-wavelength light—including UV and blue light—emitted by common sources like white LED and fluorescent bulbs.
Navigational Confusion and Artificial Light
Transverse Orientation Failure
The apparent attraction to light is a sensory malfunction caused by artificial light sources. Nocturnal flying insects, including crickets, historically relied on celestial navigation to maintain a straight flight path. This method, called transverse orientation, involves keeping a fixed angular relationship with a distant light source, such as the moon or stars. Because these natural sources are so far away, their light rays are effectively parallel, allowing the insect to travel a straight line by maintaining a constant angle to the light.
When a cricket encounters a nearby artificial light source, like a porch lamp, the system breaks down. As the insect attempts to maintain its constant flight angle relative to this source, the angle of the light rays rapidly changes with every movement. The instinctive response is to continuously course-correct, which results in a flight path that spirals inward toward the light source.
Dorsal Light Response
A related mechanism known as the dorsal light response further contributes to this disorientation. This innate reflex causes the insect to orient its dorsal (back) side toward the brightest source in its visual field, which helps maintain an upright posture. When a powerful artificial light is directly above or below the cricket, the insect’s body constantly tilts to keep its back facing the light. This leads to erratic, looping, or inverted flight patterns that often end with the cricket trapped near the source.