Empty Hive: Why They Left and Where They Went

Colony loss is a process rather than an event, and it often goes unnoticed. An empty hive can be the first indication of a problem. Honey bees are masters of adaptation and extremely resilient. They readily adjust to changes in their environment and move forward with their work as conditions deteriorate, making it difficult for the beekeeper to predict that the hive will soon be empty. Certain characteristics of colony development are integral in the rapid depopulation of a hive.

1. Lifespan is determined by the age at which a honey bee becomes a forager. Social role, not chronological age, regulates honey bee senescence. A lack of behavioral development correlates with a near lack of biological aging. Once a worker starts foraging, however, mortality rate soars and remaining life expectancy plummets to about a week or so (Visscher 1997).
2. Transition to forager is regulated by “social inhibition.” Foragers produce an inhibitor pheromone that keeps middle-aged bees working inside the hive (Leoncini 2004). When the forager population declines, those bees that no longer receive adequate amounts of pheromone switch to the task of foraging.
3. Bees with a reduced lifespan make an early transition to forager. Because the onset of foraging determines lifespan, bees with a reduced life expectancy experience accelerated behavioral development and begin foraging earlier in life (Woyciechowski 2009).
4. The needs of the colony override individual age in the division of labor. A forager may regress to nursing, as a nurse may advance to forager (Guzman-Novoa 2004).
5. Gathering of food is the colony’s highest priority. One of the defining characteristics of a colony in the throes of late-stage collapse is the abandonment of brood. The need to forage takes priority over all other jobs in the hive (Khoury 2011).

It’s clear that foraging plays a fundamental role in the population dynamics of a colony. In a heavy mite infestation, bees that were parasitized in the brood cell emerge with a normal appearance but experience a 30% or greater reduction in lifespan (Amdam 2002). This forces younger bees to forage prematurely, creating an abnormally high demand for new foragers (Robinson 1996).

Bees that begin foraging earlier in life are heavier and have underdeveloped flight muscles. The lower the age of the forager, the fewer trips made, and each trip is of longer duration (Perry 2015). One out of every three bees that forage prematurely are lost within the first 30 minutes of flight activity. Such bees were shown to have only a 20% chance of survival over a 30-minute orientation flight.

The continued recruitment of increasingly younger bees into the foraging role soon becomes an aggressive cancer and eventually causes depopulation of the brood nest (Khoury 2011). The shortage of nurse bees results in malnourished and unincubated brood, leading to a decline in birth rate. It’s a total death spiral.

In the case of mite-induced collapse, a viral epidemic has also gripped the colony. Sick bees voluntarily leave the hive and infested foragers drift to neighboring colonies (Goodwin 2006). Mite collapse is trademarked by the occurrence of dead bees half-emerged from the brood cell. Most or all soon find themselves outside the hive in a foraging role they are unable to fulfill, finally taking off on a one-way flight to nowhere.

From the outside it would appear the bees suddenly abandoned the hive and fled in an organized fashion, but that does not sync with the chaotic disaster unfolding on the inside. They disperse and die, succumbing to starvation, infection, exhaustion, exposure or predation.

Check for proper age distribution in the brood nest. Take notice of the bee-to-brood ratio. Look for young bees outside the hive where they don’t belong. Check for adequate defense at the entrance. Beware your strongest hive — high populations of bees produce high populations of mites. The best advice is to be proactive concerning mites and not to rely on snapshot assessments of colony health.