Wild Bees: masters of winter survival
Wild bees are an incredibly diverse group of insects, with nearly 500 species already recorded in Poland. This number is even higher in Switzerland, with approximately 630 species. Globally, there are about 20,000 species of wild bees. Each species has developed its own strategies to cope with harsh winter conditions. Their survival during this period depends on adapting their wintering site, metabolic rate, and development pace, as well as choosing the right life strategy. This article explores the various ways solitary bees survive the winter and their fascinating adaptations.
Bumblebees: queens hibernate alone
In Poland, only the honeybee and bumblebees produce honey. Although bumblebees make honey, they do not store it for the following winter. Entire colonies, except for young queens, perish before the cold sets in. After mating (queens store sperm in a specialized sac and release it as needed to fertilize eggs), the new queens set out to find suitable hibernation spots. They dig small burrows underground in cool, shaded locations to avoid premature awakening caused by winter sun.
Bumblebees are not resistant to extremely low temperatures, and their survival strategy is based on avoiding frost. Interestingly, studies have shown that male bumblebees tolerate cold better than females, likely because they spend more nights outdoors during their summer activities.
Carpenter bees: better together
Carpenter bees, sometimes called “black bees,” are among the largest bees in Europe. In Poland, two species are found: the violet carpenter bee and the black-horned carpenter bee. For the winter, these bees return to their nests or seek new hiding places. They typically hibernate in groups, which offers significant advantages: the temperature in group nests is higher, allowing the bees to save energy and better survive until spring.
Mason bees: solitude and extreme frosts
Mason bees, such as the orchard mason bee, hibernate as adults enclosed in cocoons. These solitary bees withstand extreme frosts—studies show they can survive temperatures as low as -30°C. This is thanks to special substances in their bodies that lower the freezing point of their bodily fluids.
For mason bees, not only frost but also its duration is crucial. High winter temperatures accelerate metabolism, leading to faster energy depletion and poorer condition in spring. Mason bees that fly longer in the season often hibernate as larvae.
The impact of climate change on wild bees’ wintering
Global warming is altering the wintering conditions for bees. Mild winters, which might once have seemed advantageous, can be problematic for some species. Higher temperatures lead to increased metabolic activity, causing bees to expend more energy.
For example, bumblebees observed in the UK are more frequently founding colonies in autumn instead of preparing for hibernation. While this behavior is an adaptation to warmer conditions, it poses risks when sudden frosts occur.
Each bee species has its own wintering strategy tailored to its lifestyle and environment. For some, surviving in freezing conditions is crucial, while for others, avoiding extreme temperatures is key. However, most bees are trying to confront the climatic challenges that may alter their established survival strategies. On one hand, all species are more or less exposed to these challenges; on the other hand, not every species may be able to adapt its strategy in response to climate changes, and in such cases, their future appears bleak.
Sources:
- Dr. Justyna Kierat, Winter Adventures of Insects, Tygodnik Powszechny
- Dr. Justyna Kierat, Solitary Bees: Warmth, Cold, naukadlaprzyrody.pl