Bees are widely recognized as busy daytime pollinators, constantly moving between flowers under the sun. This primarily diurnal activity leads many to assume that all bees retire to their nests once darkness falls. However, the question of whether bees can fly at night reveals a more nuanced reality within the diverse world of these insects.
Why Most Bees Avoid Night Flight
The majority of bee species, including common honeybees and bumblebees, are diurnal, active during daylight hours. They rely on sunlight for navigation, using the sun’s position as a celestial compass and perceiving polarized light patterns. Without this guiding light, they become disoriented, making night flight impractical and hazardous.
Foraging also presents a significant challenge in darkness. Most flowering plants, which provide nectar and pollen, are open and most rewarding during the day. Attempting to collect resources at night would be less efficient due to limited visibility of floral cues.
Night also brings increased risks from nocturnal predators like bats. Temperature regulation is another factor; bees are ectothermic, meaning their body temperature is influenced by their environment. Cooler night temperatures can reduce their activity, as they must maintain a certain body temperature for flight muscles to function efficiently.
Bees That Fly in Darkness
While most bees are grounded at night, about 1% (around 250 species) are active in low-light conditions. These bees are categorized as either crepuscular (active during twilight hours) or truly nocturnal, flying in complete darkness. Such species are more commonly found in tropical regions, where warmer nighttime temperatures and specific night-blooming flowers offer unique ecological niches.
Examples of crepuscular bees include various sweat bees from the Megalopta genus, such as Megalopta genalis, found in Central American rainforests. Other crepuscular species include squash bees (Peponapis and Xenoglossa genera) and some species within the Ptiloglossa and Caupolicana genera. Notably, some honeybee species, like the giant Asian honey bee (Apis dorsata) and certain African honey bees (Apis mellifera adansonii), can also forage during twilight and even on moonlit nights. The Indian carpenter bee (Xylocopa tranquebarica) stands out as one of the few truly nocturnal bees known to navigate even in moonless conditions.
Adaptations for Night Activity
Nocturnal and crepuscular bees possess specialized adaptations for effective operation in dim light, primarily in their visual systems. Unlike diurnal bees, nocturnal species have significantly larger compound eyes with wider facets, enhancing light-gathering. For instance, the nocturnal sweat bee Megalopta genalis has eyes roughly 27 times more sensitive to light than diurnal honeybees.
They also exhibit enlarged ocelli, three simple eyes on their heads. These ocelli are highly sensitive to light, aiding orientation and navigation in low-light environments.
Beyond optical changes, some nocturnal bees have neural adaptations that increase light sensitivity by summing photons, though this can reduce spatial resolution. They also rely more heavily on other senses, using improved olfactory capabilities to locate night-blooming flowers that emit strong scents. These multi-sensory adaptations allow a select few bee species to thrive where most relatives cannot.