Wasps are primarily active during daylight hours, unlike many nocturnal insects. This fundamental difference means their movement toward or away from light, known as phototaxis, is typically negative concerning artificial illumination. Wasps generally avoid or become disoriented by non-natural light, a behavior rooted deeply in their reliance on celestial navigation. Understanding their visual systems explains why they shun the porch light.
How Wasps Use Natural Light for Flight and Orientation
Wasp navigation depends heavily on celestial cues, using the sun and the pattern of polarized light in the sky as a large-scale compass. They employ transverse orientation, a sophisticated method requiring them to maintain a constant angular relationship with a distant light source to fly straight. Since the sun is far away, this angle remains constant, allowing for long-distance travel and accurate homing.
The pattern of polarized skylight, invisible to the human eye, is a particularly important cue. This symmetrical light pattern relates directly to the sun’s position, acting as a reliable visual guide even when the sun is obscured. Wasps rely on these ambient light cues to monitor their flight path and return to the nest.
The Mechanics of Wasp Vision and Light Perception
The wasp visual system uses five separate eyes: two large, multi-faceted compound eyes and three smaller eyes called ocelli. The compound eyes consist of thousands of light-sensing units called ommatidia, providing a wide field of view and high spatial resolution.
The three ocelli are single-lens eyes positioned in a triangle on the top of the head, sensitive to changes in light intensity. These simple eyes help the wasp sense the horizon and stabilize its flight posture, and they are also involved in detecting polarized light. Wasps perceive ultraviolet (UV) light, which is part of their trichromatic color vision system.
Wasps have a very high flicker fusion rate (CFF), the speed at which a flickering light appears continuous. Insects perceive time and motion much faster than humans due to their high CFF values. This high temporal resolution means that subtle flicker, imperceptible to humans in some artificial lights, would be highly noticeable and disturbing to a wasp.
Why Artificial Lights Disorient or Repel Wasps
The fundamental issue with artificial lights is their proximity, instantly disrupting the wasp’s celestial navigation system. When a wasp attempts to maintain a fixed angle to a close light source, the corrective flight path results in a spiraling motion instead of straight-line travel. The proximity of a porch light causes immediate navigational failure because the wasp instinctively treats the light as a distant compass.
Artificial lights also lack the precise spectral and polarization cues wasps need for orientation. Many common light sources do not emit the full spectrum of UV light, which wasps are highly sensitive to. This spectral mismatch, combined with the scattering of natural polarization signals by artificial light at night (ALAN), leads to disorientation.
This spectral mismatch and proximity error lead to disorientation, causing wasps to fly away from the confusing light source. Lights that emit a brighter, bluer, or whiter light are more disruptive because these wavelengths are closer to the UV light wasps use for navigation. The result is a negative phototactic response.
Common Misconceptions About Wasps and Light
A common belief is that wasps are strongly attracted to lights like moths, but this comparison is inaccurate. Moths are nocturnal and exhibit strong positive phototaxis, while wasps are diurnal and return to their nests when darkness falls. If a wasp is seen near a light at night, it was likely disturbed from its nest after dusk or accidentally trapped inside.
When wasps are observed near people and lights, such as during an outdoor meal, their primary motivation is not the light itself. They are instead drawn by chemical cues, specifically the scent of sugary drinks, ripe fruit, or protein-rich human food. The high sensitivity of their visual system makes artificial light sources confusing and repellent.