The discovery began with the kind of laboratory mishap that normally ruins an experiment. Water accumulated inside tubes holding dormant queen bumblebees in a refrigerator at the University of Guelph. The researchers assumed the flooded insects had died. When the water was drained, the queens began to move and recovered.
That accident produced a question with consequences far beyond the refrigerator. A queen bumblebee can spend most of winter alone below ground, in a shallow chamber exposed to rain and snowmelt. Could diapause, the deep energy-saving state that carries her through the cold season, also let her wait out a flood?
A controlled experiment with 143 common eastern bumblebee queens found that some could remain fully submerged for seven days. Seventeen of 21 queens in the longest complete-submersion group were still alive eight weeks later. Across the experimental groups, mean survival was 89.5 percent.
The numbers are more precise than the usual “bees can breathe underwater” retelling. They also have clear limits. This was one species under controlled conditions, and the study measured survival through eight more weeks of artificial overwintering, not the queens’ later ability to establish healthy colonies.
A flooded refrigerator created the first clue
Sabrina Rondeau and Nigel Raine describe the origin plainly in their 2024 Biology Letters paper. During an earlier experiment, an “experimental oversight” allowed water to fill a container holding diapausing queens. Draining the container revealed that the insects were alive.
An accident can generate a hypothesis, but it cannot test one.
The researchers therefore obtained 143 common eastern bumblebee queens, Bombus impatiens, and placed them in soil-filled tubes. The queens entered artificially induced diapause in refrigerated storage. Seven days later, the team added tap water to the treatment tubes.
Half of the water treatments allowed queens to float naturally at the surface. The other half used a plunger-like apparatus to keep them completely underwater. Within each condition, exposure lasted eight hours, 24 hours or seven days. That produced six treatment groups of 21 queens each. A further 17 queens remained dry as controls.
Once an exposure ended, each queen was moved into a fresh tube containing soil and returned to cold storage. The researchers checked survival one, four and eight weeks later. That follow-up matters: a queen that twitched immediately after removal from water but died soon afterward would not count as a durable recovery.
What the 89.5 percent survival figure actually means
Survival across all experimental groups remained high after eight weeks, with a mean of 89.5 percent and a standard deviation of 6.4 percentage points. Statistical analysis found no detectable effect of treatment regime or exposure duration. Queens left floating and queens held underwater did not separate into clearly different survival outcomes, nor did the eight-hour, 24-hour and seven-day groups.
The most demanding group makes the result tangible.
Of 21 queens kept completely underwater for seven days, 17 were alive eight weeks later, or 81 percent. Among 17 dry controls, 15 survived, or 88 percent. The experiment did not detect a statistically significant difference between them.
Queen weight did matter. Heavier queens had a higher probability of survival, consistent with a broader literature linking body condition to the difficult months of diapause. A separate field study of common eastern bumblebee queens found high early overwinter survival but a decline across six months, underlining that a week-long flood is only one part of a long seasonal filter.
The title’s 89.5 percent is therefore a group-level experimental summary, not a promise that 89.5 percent of all flooded queens in nature will live. Real burrows differ in soil, temperature, water chemistry, microbes, oxygen, sediment and the speed at which water arrives or recedes.
One sleeping queen contains a colony’s only possible beginning
A bumblebee colony is annual in temperate regions. Workers, males and the old queen generally die as the season closes. Newly produced queens mate, build energy reserves, disperse and find protected places underground or beneath debris. Each enters diapause alone.
Spring survival does not merely add one insect back to the population. The emerging queen must feed, locate a nest cavity, build the first brood cells, lay eggs and provision her larvae. Only after the first workers mature can they assume much of the foraging and nest work.
That timing also connects a hidden winter insect to the plants waiting above ground. ScienceBlog previously reported early-season pollination deficits when bumblebee queens were still hibernating. A queen must survive the soil and return when flowers can support her first brood.
If the queen dies underground, the colony she would have founded never begins. Flood tolerance could buy that unwritten colony enough time for water to drain. It is a plausible ecological value of the trait, but it was not measured directly. The 2024 team did not track nest founding, egg laying, worker production or reproductive output after the queens emerged.
That distinction matters in a field already full of overlapping pressures. ScienceBlog has previously covered evidence that excessive nest heat may constrain bumblebee populations and that temperature and precipitation help shape wild-bee abundance. Showing tolerance to one form of inundation does not cancel heat, habitat, pesticides, pathogens or food shortages.
Two years later, researchers found three ways the queens endure water
The original study established survival but did not resolve the physiology. A 2026 Proceedings of the Royal Society B study by Charles-A. Darveau, Rondeau and Skyelar Rojas returned to diapausing B. impatiens queens with respirometry and biochemical measurements.
The submerged insects continued producing carbon dioxide for four and eight days, while dissolved oxygen in the surrounding water declined. Together, those measurements show that the queens were exchanging gases underwater. They were not simply sealing their breathing openings and surviving on a fixed pocket of air.
A likely aid is a very thin air layer held against the hairy body, through which oxygen from water can diffuse toward the insect’s tracheal breathing system. The study established underwater gas exchange, but the exact physical route still needs direct testing.
Respiration was only part of the answer. Submerged queens accumulated lactate, evidence that they also made energy anaerobically. At the same time, their metabolic demand fell to an extraordinarily low level. Diapause had already reduced energy use by more than 99 percent from an active state; submersion depressed it further.
After the queens returned to air, metabolic rate rose sharply and then moved back toward its earlier level over about a week as lactate declined. Survival was therefore not the same as being unaffected. The insects entered a measurable recovery period after resurfacing.
The study does not make every bumblebee flood-proof
Bombus impatiens is widespread across eastern North America and commonly used in commercial pollination and laboratory research. It is considered relatively robust compared with several declining bumblebee species. The experiment cannot establish that queens from other species, climates or evolutionary histories share the same tolerance.
It also tested a single inundation episode lasting no more than seven days in the survival study. Repeated flooding, longer exposure, warmer water, depleted oxygen, contaminants and abrasive sediment could produce different outcomes. Floods may destroy a hibernation chamber, expose a queen to predators or leave her without suitable spring flowers even if she survives underwater.
Climate change makes this caution more important. Heavier precipitation can increase flood risk in some regions, but local outcomes depend on season, soil, drainage, snowpack and land use. A laboratory capacity is one input into that problem, not a population forecast.
Nor should “hibernating” be taken too literally. Researchers often use the familiar word for readers, but diapause is a regulated physiological state rather than ordinary sleep. The queen’s deeply suppressed metabolism is central to the underwater result and gives no reason to expect an active foraging bumblebee to tolerate the same treatment.
The next test begins after the queen wakes
The 2024 experiment replaced an assumption with evidence: complete inundation does not necessarily kill a diapausing common eastern bumblebee queen, even when it lasts a week. The 2026 work added a mechanism involving underwater respiration, anaerobic metabolism and still deeper metabolic depression.
What remains unknown is just as important. Researchers need tests across other bumblebee species, realistic soils and water conditions, repeated flood cycles and longer natural winters. Most of all, they need to follow survivors into spring and measure nest founding, brood production and the eventual creation of new queens.
An animal can survive an ordeal yet pay for it later in depleted energy or reduced reproduction. Until those outcomes are measured, “buying a future colony time” should be read as a biologically grounded possibility, not a demonstrated colony-level result.
The accidental flood still revealed something difficult to see from above ground. Beneath winter soil, the only living founder of a possible colony can spend days under water, return to air and continue waiting for spring.