Dead bees in front of the hive: causes and diagnosis

Dead bees on the landing board or in the grass in front of a hive almost always cause alarm. Yet this observation is not a diagnosis: it is a symptom, which may reflect something entirely normal, a serious disease, starvation or poisoning. The whole point is to read correctly what you see, then respond with the right level of urgency.

This factsheet follows a decision tree: what to observe, the possible causes from the most common to the rarest, how to tell them apart, then what to do.

What to observe before drawing conclusions

Before looking for a cause, answer a few questions: they are what steers the diagnosis.

1. How many? A few dozen bees, a handful, or a real carpet? In France, the official definition of an acute mass mortality starts at more than one litre of dead or dying bees per colony¹.
2. How many colonies? A single hive, a few, the whole apiary, or even several apiaries in the area?
3. Since when? A sudden onset over one or two days, or a gradual build-up over weeks?
4. Which bees? Workers, drones, young bees that have barely emerged, larvae or pupae, a queen?
5. What do they look like? Whole or mutilated bees, normal or black and shiny, deformed or splayed wings, swollen abdomen, tongue sticking out?
6. What are the living bees doing? Normal activity at the entrance, bees trembling, crawling or spinning on the spot, fighting at the entrance?
7. What is the context? Season, weather over the last few days, colony stores, recent treatments, farm work nearby.

Write down these answers, with the date and hive number, and take photos.

Possible causes, from the most common to the rarest

1. Normal mortality and hive cleaning

In season, a worker lives only a few weeks. Most foragers die away from the hive, some inside. Specialised workers, the “undertakers”, grab the corpses, carry them out and drop them outside the hive⁴. A few dead bees in front of the entrance are therefore commonplace.

In late winter, this is more visible. On the first mild days the colony clears out the bees that died over winter, and cleansing flights leave exhausted bees on the ground or on snow. A small pile in front of an active colony that is bringing in pollen is usually nothing to worry about.

2. Drone eviction

In late summer and autumn, as resources dwindle, workers stop feeding the drones and drive them out of the hive⁵. Unable to feed themselves, the drones die in front of the entrance. They are easy to recognise: bigger and stockier than workers, with very large eyes that meet on top of the head. This is normal.

A colony that keeps its drones late into autumn, unlike its neighbours, may have lost its queen.

3. Varroa and viruses

This is the most common disease-related cause. In France, during visits carried out between 2017 and 2023 by the Observatory of honey bee mortality and weakening (OMAA) for problems other than acute mass mortality and regulated diseases, varroosis was the most frequent conclusion (51% of visits), followed by viral diseases (36%). Chronic bee paralysis virus was the virus most often involved, found in 24% of visits².

The picture depends on the virus:

• Chronic bee paralysis: bees that tremble, cannot fly and crawl on the ground; some are black, hairless and shiny. Dead bees pile up in heaps right outside the entrance, sometimes by the thousand, whereas with poisoning they tend to be spread across the apiary⁸. The disease often affects one or a few colonies, and favours populous, confined colonies^{8, 9}.
• Deformed wing virus: young bees with crumpled wings and a short abdomen, thrown out of the hive. It signals an already high varroa infestation.
• Acute bee paralysis and related viruses: dying bees and a colony that weakens fast in late summer, linked to high varroa levels.

Mortality then builds up over weeks, and a mite count often provides the answer.

4. Starvation

Starvation is still a common cause: 10% of OMAA visits concluded that the colony lacked food². It strikes mostly in spring, during cold or wet spells, when the colony uses up its last stores to rear brood. The strongest colonies are often the most at risk, because they consume the most⁶.

The signs: empty cells around the brood, lethargic bees, many dead bees head-first in the cells, nibbled brood cappings and pupae thrown out of the hive⁶. A colony can die very quickly once it reaches this stage. In winter, the cluster can also starve a few frames away from its stores, trapped by the cold: see Winter colony losses.

5. Cold and chilled bees

In spring, a sudden cold snap or a shower catches foragers, which die numbed on the ground, sometimes right in front of the hive. The weather explains it, the colony stays active, and the phenomenon stops when fine weather returns.

6. Robbing

When nectar flows stop, in late summer and early autumn, strong colonies attack weak ones to steal their stores. The signs: zigzag flight in front of the hive, fighting at the entrance, more dead bees on the landing board, a greasy, sticky entrance⁷. Wax debris completes the picture. Robbing can empty a colony in a few days and spreads disease.

7. Poisoning

Poisoning is the most feared cause, but not the most common. Of the reports received by the OMAA between 2017 and 2021, about 9.5% were routed to the acute mass mortality surveillance scheme³, and poisoning was retained in only 5% of visits for other problems².

It is recognised first by its timing: sudden mortality, within hours or days, affecting several colonies at once, often at the time of sowing or a nearby spray. Dying bees tremble, spin on the spot and sometimes have their tongue sticking out. A study near maize fields found a seed-treatment insecticide in dead bees collected in front of hives in spring¹². See the Pesticide poisoning factsheet.

8. Predators

• Asian hornet: it hunts foragers by hovering in front of the hives¹¹. It carries its prey away and leaves few corpses, but the stressed colony stops foraging. See Asian hornet.
• Wasps: in late summer, they rob weak colonies.
• Mice and shrews, in winter: headless bees or bees with a pierced thorax, small heaps of wings and legs, gnawed comb debris in front of the entrance. See Mice and rodents.

9. Other diseases of adult bees

• Nosema and dysentery: sluggish bees, swollen abdomen, diarrhoea stains on the hive front and frames, especially in late winter.
• Tracheal mite: bees crawling on the ground near the hives, wings splayed in a “K”, mainly in winter and early spring. These signs are not specific: only dissection of the tracheae confirms the mite¹⁰.

10. Rare causes

• Suffocation or overheating: a hive closed for too long in hot weather, during transport or a nearby spray, or poorly ventilated.
• Treatment error: a medicine used incorrectly or an unauthorised product.
• Dead queen in front of the entrance: after supersedure, a fight between young queens or handling. The colony may be queenless.

How to tell the causes apart

Several causes can combine: in OMAA visits, nearly a third concluded that several factors were involved, most often varroosis together with a viral disease².

What to do, step by step

1. Observe and record the answers to the questions above, with photos.
2. Compare with the other colonies in the apiary: a single affected hive points to a colony-specific cause (disease, starvation, robbing); several hives suddenly affected point to an external cause.
3. Open the colony if the weather allows: stores, brood, presence of the queen or young eggs, appearance of the bees on the frames.
4. Count mites, unless poisoning is obvious: a high result points to varroa and its viruses.
5. If poisoning is suspected: take samples and report without delay (see below).
6. Deal with the cause: feed in case of starvation, reduce the entrance in case of robbing, treat against varroa, unite a colony that is too weak.
7. Ask for help if the picture remains unclear: a vet or a bee health technician.

Laboratory diagnosis

Tests confirm a hypothesis: viruses, Nosema, tracheal mites or pesticide residues. For suspected poisoning, the reference French guidance requires sampling dying or freshly dead bees within 48 hours, if possible as three samples of about 50 g, or around 500 bees: one for analysis, one sealed for the beekeeper, one for the authorities. Samples travel chilled, then are stored in a freezer at about -20 °C. A sample of around a hundred bees may be added for disease testing¹.

Regulations

What follows applies to France; rules vary between countries, so check those that apply where you keep bees.

• Acute mass mortality: more than one litre of dead or dying bees per colony, or depopulation not due to swarming, appearing suddenly in under 15 days, in at least 20% of the colonies in the apiary (1 colony in an apiary of 2 to 5, 2 colonies in an apiary of 6 to 10)¹. It is reported to the DDPP (departmental veterinary services) or, in regions where it operates, to the OMAA single desk, which passes it on to the authorities¹. The regional desk’s number is on the DRAAF website.
• Regulated diseases: any suspicion of American foulbrood, Nosema apis, Aethina tumida or Tropilaelaps must be reported to the DDPP¹.
• Gradual weakening and winter mortality without a precise timeline fall outside the acute mass mortality scheme: a vet or the local bee health organisation then takes over¹.

The most common mistakes

• Panicking over a few dead bees in late winter or over drones evicted in autumn.
• Conversely, waiting several days in the face of sudden mortality across several hives: the evidence of poisoning disappears.
• Concluding poisoning without opening the hive: varroa, viruses and starvation explain mortality far more often.
• Forgetting stores in spring: a strong colony can starve in a few days.
• Feeding outside or leaving honey frames lying around, which triggers robbing.

Frequently asked questions

How many dead bees in front of a hive is normal? There is no fixed figure. A few dozen bees in front of an active colony, especially in late winter, are commonplace. What should alert you is a number that rises from day to day, one hive clearly more affected than the others, or a carpet approaching a litre.

Why are there hardly any dead bees when my colony is dwindling? Sick or poisoned bees often die away from the hive, while foraging. A colony can therefore melt away without heaps of corpses. Sudden depopulation not due to swarming is in fact part of the official French definition of acute mass mortality.

Only one hive is affected: could it be poisoning? It is possible, but less likely. Mortality limited to one colony points first to a cause specific to that colony: chronic bee paralysis, varroa, starvation or robbing.

References

1. French Ministry of Agriculture, DGAL (2018). Note de service DGAL/SASPP/2018-444: surveillance des mortalités massives aiguës d'abeilles adultes avec hypothèse d'intoxication. draaf.bretagne.agriculture.gouv.fr
2. Plateforme ESA, OMAA, Delmar E. et al. (2025). Analyse des visites « Autres troubles » (2017-2023). plateforme-esa.fr
3. Plateforme ESA, OMAA monitoring group (2023). Analyse des déclarations de troubles de santé à l'Observatoire des mortalités et des affaiblissements de l'abeille mellifère (2017-2021). plateforme-esa.fr
4. Visscher P.K. (1983). The honey bee way of death: necrophoric behaviour in Apis mellifera colonies. Animal Behaviour 31(4): 1070-1076.
5. Free J.B., Williams I.H. (1975). Factors determining the rearing and rejection of drones by the honeybee colony. Animal Behaviour 23: 650-675. doi.org
6. Wilkinson D. National Bee Unit (APHA). Starvation of honey bees: recognition and prevention. nationalbeeunit.com
7. EU CAP Network, Horizon Europe project « Best Practices and Innovations for a Sustainable Beekeeping » (2022-2026). Practice abstract: reduce risk of robbing. eu-cap-network.ec.europa.eu
8. Budge G., Stainton K. (2016). Chronic bee paralysis. Bee Craft, September 2016 (article distributed by the National Bee Unit). nationalbeeunit.com
9. Ribière M., Olivier V., Blanchard P. (2010). Chronic bee paralysis: a disease and a virus like no other? Journal of Invertebrate Pathology 103 (Suppl. 1): S120-S131. doi.org
10. Sammataro D., de Guzman L., George S., Ochoa R., Otis G. (2013). Standard methods for tracheal mite research. In: The COLOSS BEEBOOK, Vol. II. Journal of Apicultural Research 52(4). doi.org
11. Monceau K., Bonnard O., Thiéry D. (2014). Vespa velutina: a new invasive predator of honeybees in Europe. Journal of Pest Science 87: 1-16. doi.org
12. Krupke C.H., Hunt G.J., Eitzer B.D., Andino G., Given K. (2012). Multiple routes of pesticide exposure for honey bees living near agricultural fields. PLoS ONE 7(1): e29268. doi.org
13. Public domain photographs: USGS Bee Inventory and Monitoring Lab, « Apis mellifera, F, face, Maryland, Beltsville » and « Honeybee drone, m, back, MD, PG County » (usgs.gov/media/images). usgs.gov

Updated : October 9, 2026
Written by : Apisanitas editorial team
Reviewed by : Review in progress