Why it starts
Robbing is a dearth behavior. While nectar is coming in, foragers work flowers because flowers are easier. When the flow stops and nothing replaces it, the calculation changes and a hive full of ripe honey becomes the best forage in range.
Penn State Extension puts the Pennsylvania dearth in July, once the summer flows diminish, and notes that colonies become more defensive of their stores then, with strong colonies starting to rob smaller or weaker ones. Your own dearth will land somewhere else in the year. The forage calendar will tell you when, which is worth knowing in advance rather than working out from the noise in the yard.
A review in Insects by Wang and colleagues lists what tips a dearth into actual robbing, and most of the list is us: opening hives too often during a dearth, which releases honey scent; feeding badly or too late; entrances left wide on colonies that cannot defend them; and not spotting the weak, queenless or diseased colony that becomes the target. The bees supply the motive. The beekeeper usually supplies the opportunity.
Telling robbing from a busy entrance
This is the part people get wrong, usually in the reassuring direction. A strong colony on a good day is loud and busy, and a first-year beekeeper looking at an orientation flight can easily talk themselves into a panic. The three are genuinely easy to tell apart once you know what you are looking at.
| What you see | What it means |
|---|---|
| Bees landing, walking straight in, ignored by guards. Many carrying pollen. | Foraging. Nothing wrong. |
| A cloud of bees hovering and facing the hive, drifting slowly, same time each afternoon, no fighting. | Orientation flight. Young bees learning the address. A good sign. |
| Bees weaving side to side across the face of the box, probing corners and cracks rather than the entrance. | Robbers looking for a way in. |
| Pairs of bees locked together, rolling on the landing board or in the grass. Dead bees below the entrance. | Robbing, in progress. |
| Flecks of wax on the landing board, and chewed, ragged cappings on the comb inside. | Robbing, and it has been going a while. |
| Bees leaving heavy and climbing away slowly, when nothing is in bloom. | They are leaving with somebody else's honey. |
The single quickest check is the guard reaction. At a healthy entrance, arrivals are waved through. During robbing, arrivals are challenged, and you will see the challenges.
The first five minutes
Speed matters more than elegance here. In rough order:
- Close the hive you are working on, now. Whatever you were part way through can wait. An open hive during a dearth is an advertisement.
- Shrink the entrance to a single bee width. An entrance reducer on its smallest setting, or a handful of grass stuffed in the gap, which works and costs nothing. The widely used rule of thumb is to give a colony no more entrance than it has guards for.
- Block the other ways in. Robbers probe every seam. Check the inner cover hole, a warped box joint, a crack under the telescoping lid, and the gap round a badly-fitted mouse guard.
- If it is already a roar, throw a wet sheet over the whole hive. This is a long-standing beekeeper's trick rather than anything from a study, and the reasoning is that robbers give up on a hive they cannot find. The residents work their way out from under it within an hour or two, and the wet cloth keeps them cool while they do. Leave it on for the rest of the day.
- Fit a robbing screen if you have one. A robbing screen puts the real entrance somewhere the residents learn and the robbers do not, since robbers home in on the scent at the front. Penn State Extension names them, along with fewer inspections during a dearth, as the two things that reduce robbing.
What not to do: do not open the lid for a look. Do not smoke the entrance heavily and hope, as it masks scent briefly and does nothing about the hundreds of bees already inside. And do not move the hive away in the middle of it, since the flying residents come back to an empty stand and the robbers simply follow the smell.
Not starting it in the first place
- Know when your dearth is and treat those weeks differently. Shorter inspections, fewer of them, entrances already reduced before you need them.
- Feed inside, late and clean up. Never at the entrance, never in the open. The Wang review recommends feeding at night during scarcity for exactly this reason. A spilled cup of syrup on the grass will start a war.
- Match the entrance to the colony. A nucleus or a recently split colony cannot defend a full-width entrance in a dearth and should not be asked to.
- Keep the yard tidy. Burr comb, scrapings, a wet extractor, supers stacked outside. All of it is bait.
- Space the hives. The Wang review suggests roughly one to two meters between hives in a row and two to three between staggered rows, which also cuts down on drifting.
- Deal with the weak colony. A queenless, failing or badly infested colony is the target that gets the whole yard going. Combine it, requeen it, or move it out, but do not leave it sitting there full of honey it cannot defend.
The part that actually costs you: mites
Losing a few pounds of honey is annoying. What robbing really does is move varroa around the yard, and the evidence on this is better than most beekeepers realize.
David Peck and Thomas Seeley, in PLOS ONE in 2019, set up colonies at one meter, fifty meters and three hundred meters from colonies that were collapsing under heavy mite loads. When the collapsing colonies were robbed out in late September, mites in the receiver colonies rose from an average of 9.0 to 23.5 per 300 bees in under three weeks. The surge tracked the robbing, not the donor colonies' peak infestation. And distance barely mattered: there was no significant difference between the colonies at one meter and those at three hundred.
Their conclusion was that "mite bombs" is the wrong picture, because it suggests mites being flung outward from a dying colony. What actually happens is that your bees go and fetch them. They proposed "robber lures" instead, and it is a better name: a collapsing colony is not exploding, it is advertising.
Two things follow from that. First, a dead or dying colony in your yard is not something to deal with next weekend. Close it up or take it away the day you find it, before it gets robbed out. Second, if a robbing event happens in your yard, do a mite wash on the robbers a couple of weeks later, not just on the colony that got robbed. The winners of a robbing fight are the ones that brought something home.
The Wang review makes the same point more broadly: robbing raises the transmission of pathogens between colonies, varroa and nosema among them, and it lists queen injury or death and outright colony collapse among the consequences for the colony being robbed. It also reports an episode in Himachal Pradesh over 2001 and 2002 in which robbing was associated with colony losses ranging from 15 to 75 percent across affected apiaries.
Where beekeepers disagree
Robbing screens are the honest argument here. Everybody agrees they work against robbers. Some experienced beekeepers put them on every colony through the dearth as a matter of course. Others fit them only when there is trouble, on the grounds that a screen also slows the residents down, confuses returning foragers for a day or two, and is one more thing to store and maintain across a lot of hives.
Both positions are defensible and the answer depends on your scale and how bad your dearth gets. If you keep a handful of colonies in a garden and you have watched a nuc get stripped once, fit the screens and stop thinking about it. If you run yards of thirty, the entrance reducer plus discipline about when you open hives will get you most of the way for none of the effort.
Sources and further reading
- Peck DT, Seeley TD (2019). Mite bombs or robber lures? The roles of drifting and robbing in Varroa destructor transmission from collapsing honey bee colonies to their neighbors, PLOS ONE. The distance experiment and the mite counts quoted above.
- Wang et al. (2025). Honey Robbing: Causes, Impacts and Preventive Measures, Insects 16(1), published online December 2024. A review of what triggers robbing and what to do about it, including hive spacing and night feeding.
- Penn State Extension: Honey Bee Management Throughout the Seasons. The July dearth, robbing screens and limiting inspections.
- Oregon State University Extension, EM 9211: Protecting honey bees from yellowjacket wasps. Wasps are a different problem with the same defenses, and the entrance advice carries over.
Log a robbing event in your hive records with the date. If mites climb in that yard six weeks later, you will want to know exactly when the robbing happened.