The question of whether hornets can navigate and operate effectively in the dark is common, sparking curiosity about their unseen world after sunset. Understanding hornet vision provides insights into their behavior outside of daylight hours.
The Mechanics of Hornet Vision
Hornets, like many insects, possess compound eyes made of numerous individual visual units called ommatidia. Each ommatidium has its own lens and photoreceptor cells, collecting light from a specific point. The combined input from thousands of these units allows hornets to perceive a wide field of view and detect motion, crucial for hunting and navigating during the day.
Hornets also have three simple eyes, called ocelli, located on top of their heads between the compound eyes. These ocelli do not form detailed images but detect changes in light intensity. They help hornets maintain flight stability and orient themselves by sensing light direction during daylight hours.
Can Hornets See in Low Light?
Hornets, particularly species like the European hornet, are known to be active and fly in dim twilight and even at night. Despite this nocturnal activity, their eyes do not exhibit specific anatomical adaptations for vision in dim light that are typically found in truly nocturnal insects. Studies suggest that the eyes of European hornets are optically less sensitive than those of some diurnal wasps.
The ability of hornets to operate in low light appears to stem from a trade-off between image resolution and light sensitivity inherent in compound eyes. While their individual ommatidia may not be highly sensitive, their relatively large body and eye size allow for neural pooling strategies. This means that signals from multiple photoreceptors can be combined in the brain, increasing overall light sensitivity at the expense of perceiving fine details. This strategy contrasts with many nocturnal insects, which often possess specialized eye structures to enhance light capture.
Nocturnal Habits of Hornets
Hornets are primarily diurnal, meaning they are most active during the day, but many species, including the European hornet, exhibit activity after dark. This nocturnal behavior includes continued hunting and foraging, as nocturnal prey like moths provide a food source. Hornets also engage in activities such as maintaining and expanding their nests at night.
A common observation is hornets being attracted to artificial light sources. This attraction can cause them to fly into windows or hover around porch lights, often due to confusion in their navigation systems, which typically rely on natural light cues. The warmth emitted by light fixtures can also draw them in, especially as temperatures drop after sunset. Despite their activity at night, hornets are still capable of defending their nests, making it unsafe to approach or disturb a hornet nest at night.