October 11, 2026 · 4-minute read
Brown marmorated stink bug in Monaco: stop the autumn invasion
From October to mid-November, the brown marmorated stink bug seeks to overwinter in heated homes. How to spot it, keep it out and never crush it.
The brown marmorated stink bug (Halyomorpha halys), native to East Asia, has spread across Europe and is now established on the Côte d'Azur, Monaco included. Between early October and mid-November, it actively looks for heated buildings in which to spend the winter: this is its critical infiltration period.
1. Recognising the brown marmorated stink bug
- Size: around 12 to 17 mm
- Shape: a broad, flattened shield
- Colour: marbled brown, mixing beige and dark brown
- Antennae: brown, with characteristic pale bands
- Edge of the abdomen: alternating dark and pale bands
- Smell: foul when crushed (often compared to rancid coriander), and long-lasting
Do not confuse it with the southern green stink bug (Nezara viridula, light green, harmless to humans) or with the forest bug (Pentatoma rufipes, uniformly brown, a harmless native species). And it has nothing to do with bed bugs, which bite and live in bedding: the brown marmorated stink bug does not bite people.
2. Why the peak falls between October and mid-November
Biology. The brown marmorated stink bug spends the winter in diapause (a form of hibernation) as an adult. To survive, it has to find a dry, dark and sheltered refuge before the first cold spells.
Ways in. As soon as the days shorten and the nights turn cooler, it looks for:
- badly fitting window seals
- roller shutters (the gap at the top of the shutter box)
- ventilation grilles and mechanical ventilation outlets
- false ceilings and loft spaces
- cellars and basements accessible from outside
- gaps behind blinds or pergolas
Gregarious behaviour. Brown marmorated stink bugs gather together to overwinter, attracted in particular by an aggregation pheromone: where a few individuals have found shelter, others follow. An infiltration left untreated in October can mean many individuals spread throughout the house by November and December.
3. The 5 things to do before the end of October
G1 — Check and redo the seals on exterior joinery. Windows, French windows, skylights: a worn rubber seal is an ideal way in for stink bugs.
G2 — Fit fine mesh over ventilation openings. Install a fine-mesh, mosquito-net-type grille over external ventilation openings (mechanical ventilation, kitchen and bathroom vents), taking care not to block them.
G3 — Seal roller shutters. The gap at the top of the shutter box is one of the most common entry points. The solution: a brush seal or special foam for shutter boxes.
G4 — Inspect loft spaces and false ceilings. A visual check, then vacuuming up any individuals left over from the previous year.
G5 — Set up specific pheromone traps. We install traps specific to Halyomorpha halys on terraces and balconies, particularly on sunny façades, where stink bugs like to land in autumn. These traps always go outside, never inside the home.
4. If you already find them indoors
Never crush one: it releases a foul-smelling secretion that lingers on clothes and surfaces.
The right ways to catch them:
- a vacuum cleaner with a HEPA filter (then empty the bag outside, in a sealed bag)
- a glass and a piece of card: catch it, then release it outside, far from the building
- wide adhesive tape: pick it up gently, without squeezing its body
- a bottle filled with soapy water: it falls in and sinks to the bottom
Contact MPS if you find several every day, or in several rooms: it is a sign of an established infiltration, and professional treatment becomes worthwhile.
5. The MPS "Brown Marmorated Stink Bug Monaco" protocol
Free on-site audit: visual inspection, identification of the species (to rule out any confusion with a native stink bug) and location of entry points. Then: professional vacuuming with a HEPA filter of the individuals present, specific pheromone traps placed outside, sealing of the entry points identified, and advice on adjustments if needed (shutters, joinery).
End of season (March to April, as they come out of diapause): a follow-up visit to check that no population has survived in isolated loft spaces.
In apartment buildings, the entry points often concern the common areas (loft spaces, service ducts, cellars): an approach coordinated with the building's managing agent is more effective than acting flat by flat. Like all our interventions, this protocol follows our 4-step method: a free audit, a personalised action plan, a discreet intervention, then a report in your client area.
6. Take stock before winter
Key takeaway: the brown marmorated stink bug is harmless to humans (no bites, no disease) but very unpleasant (smell, proliferation). From October to mid-November is the time to act: after that, the infiltration is established for the whole winter. A diagnosis, sealing the entry points and specific traps are the best way to avoid the problem the following winter.
See also our seasonal prevention advice. After a visit or an initial conversation, we draw up a detailed quote, free and without obligation.
Request your free quote or call +377 37 70 70 02: reply within 6 hours.
Frequently asked questions
- Does the brown marmorated stink bug bite people?
- No. It feeds on plants and fruit, does not bite people and does not transmit disease: its presence is mainly unpleasant, because of its smell and its numbers.
- I crushed one by accident: how can I limit the smell?
- Air the room, wash any affected fabrics promptly and clean hard surfaces. The smell is persistent: in future, catch them with a glass or a vacuum cleaner with a HEPA filter instead, and never crush them.
- Do pheromone traps work?
- Yes, as a complement: placed outdoors, they help to gauge the pressure and catch some of the stink bugs before they get in. On their own they are not enough on a poorly sealed building, hence the importance of sealing entry points: for a free audit, call +377 37 70 70 02.
