Bees are primarily known for daytime foraging, diligently collecting nectar and pollen. Diurnal behavior, active during daylight, characterizes most bee species worldwide. While many associate bees with buzzing through sunlit gardens, fascinating exceptions and complex nocturnal activities occur within their hives. This article explores why most bees are active during the day, the unique species that defy this norm, and the work that continues inside the hive after dusk.
Why Most Bees Aren’t Active at Night
Most bee species are not active after dark due to several environmental and physiological factors. Bees rely on light for navigation, using direct sunlight and polarized light patterns to locate food and return to nests. Their vision is not well-suited for low-light conditions, making foraging and safe flight difficult once darkness falls. Foraging bees are sensitive to light cues that signal available work time.
Temperature also limits nighttime activity. Bees are ectothermic; their body temperature and activity levels are regulated by their environment. Most bee species require temperatures above approximately 13°C (55°F) for active foraging, with optimal activity often occurring closer to 19°C (66°F). Nighttime temperatures frequently drop below these thresholds, hindering their ability to fly and metabolize efficiently.
Many flowers, primary food sources for bees, close their blossoms or cease nectar and pollen production at night. The risk of encountering nocturnal predators also increases, deterring venturing outside the hive.
Nocturnal Bee Species
While most bees are diurnal, about 1% (250 species) are crepuscular or nocturnal. These include “sweat bees” from genera like Lasioglossum and Megalopta (e.g., Megalopta genalis, Megalopta centralis). Some carpenter bees, such as Xylocopa tranquebarica, and the Giant Asian Honey Bee (Apis dorsata) have been observed foraging at night.
These bees have specialized adaptations for low-light navigation and foraging. A notable adaptation is their larger ocelli (simple eyes), more efficient at gathering limited light. For instance, the eyes of Megalopta genalis are reported to be 27 to 30 times more sensitive to light than those of their diurnal counterparts. They also utilize neural processing to enhance their vision from minimal light input.
Nocturnal bees typically forage on night-blooming flowers, which often have pale petals reflecting moonlight and strong scents to attract pollinators like moonflowers and evening primroses. This nocturnal foraging also offers reduced competition from diurnal bees.
Bee Behavior Inside the Hive After Dark
Even when external foraging ceases, a beehive remains active throughout the night. Bees engage in various tasks contributing to the colony’s health. Most bees, including honey bees, rest and sleep for 5 to 8 hours nightly. During this rest, their antennae may droop, and their bodies adopt a relaxed posture. Younger worker bees, like nurse bees, often have less structured sleep and may be active at any time, attending to colony needs.
Brood care is a significant nighttime activity, where young worker bees feed larvae and cap cells containing developing bees. Bees also process the nectar collected during the day into honey. This involves fanning wings to evaporate excess water from nectar, creating an audible hum or “roar” near the hive entrance.
Maintaining the hive’s internal temperature (thermoregulation) is another nocturnal duty. Bees work collectively to regulate warmth, clustering to conserve heat, particularly in cooler conditions. They strive to maintain the brood comb temperature within a narrow range, typically between 33 and 36°C (91 and 97°F), to support the healthy development of their young.