Below is a month‑by‑month overview of Yellow‑legged (Asian) hornet behaviour in the UK, based on the species’ established life cycle and UK‑specific observations from DEFRA, the National Bee Unit, and beekeeping organisations. This reflects current UK conditions, where the species is not yet fully established but is appearing more frequently.

Monthly Behaviour in the UK

January – February

• Only fertilised queens survive winter, hidden individually in sheltered places (soil, sheds, bark, buildings).
• No nests or worker activity.
• Hornets are inactive and very rarely seen.

March

• In mild springs, queens emerge from hibernation.
• Queens feed on tree sap, nectar, or fallen fruit to regain strength.
• Suitable areas: gardens, parks, woodland edges.
• This is the earliest realistic time sightings occur in southern England.

April

• Queens begin building primary (embryo) nests, often small and hidden:
  • Sheds, hedges, roof eaves, garages, bird boxes.
• Egg‑laying starts; queen does all foraging and care.
• Key detection window for monitoring and trapping queens.

May

• First worker hornets emerge.
• Workers take over foraging and nest expansion.
• Queen remains in the nest laying eggs.
• Hunting pressure on insects begins to increase but is still limited.

June

• Colony growth accelerates.
• Secondary nests may begin forming, often higher in trees.
• Workers become more visible.
• Predation on bees increases around apiaries.

July

• Nests grow rapidly and may reach football size or larger.
• Intensive hawking behaviour outside beehives (hovering and catching bees).
• Worker numbers rise into the hundreds or thousands.
• Public sightings become more common.

August

• Peak activity month.
• Very high impact on honey bees and other insects.
• Large secondary nests often high in trees or buildings.
• Hornets are active all day but not at night.
• Most UK nest discoveries happen from August onwards.

September

• Colonies produce new queens and males.
• Feeding demand is highest.
• Aggression near nests increases (defensive behaviour).
• Critical time for nest finding and destruction to prevent overwintering queens.

October

• Mating occurs.
• Fertilised queens leave the nest to seek overwintering sites.
• Worker numbers start to decline.
• Old nests begin to fail.

November

• Remaining workers and males die off naturally.
• Old nests become inactive and are not reused.
• Only hibernating queens remain alive.

December

• Complete dormancy.
• No visible hornet activity.
• Risk resumes the following spring if queens survive.

Key UK Notes

• Asian hornets are not yet established in the UK, but overwintering has now been confirmed in southern England.
• Early spring queen control (March–May) is the most effective prevention strategy.
• Any sighting should be reported using the Asian Hornet Watch app