Why do these bugs overwinter in the house?
UMass Extension says these insects overwinter in homes, office buildings, sheds and warehouses. A warm, sheltered space under the roof gives them the place to spend the cold months, and the attic and upper rooms are where that space is found.
The insect looks for a sheltered place in the cooler months, and the attic offers one. The roof holds some warmth from the sun on the autumn days, and the space is dark and still. The insects come in through the roof line and settle along the boards and in the corners, where the temperature changes slowly.
The rooms beneath follow. An insect that enters at the top can move down through a wall void or a gap around a pipe, and it turns up in the closets and corners of the rooms just below the roof. That is why the walk for these insects starts at the top of the house.
What does the odour mean for the homeowner?
UMass describes these bugs as harmless to people and pets, and their main nuisance is the odour they give off when disturbed. The odour can cling to fabric and linger in a room.
The odour is a defence the insect releases when it is squashed, handled or disturbed. A homeowner who crushes one may notice the smell for some time. The insects do not bite or sting people, and the UMass account does not describe a health risk from them.
The safe way to deal with the bugs is the vacuum. A shoe or a cloth applied to a bug releases the odour and leaves a mark, and the bag should be sealed and removed from the house after vacuuming.
How are the entries found?
The entries are found at the roof line: the eave where the roof meets the wall, the gable vent, the soffit joint and any roof penetration. A gap in one of those lets the insects into the attic space.
From the ground the technician checks each eave and gable for a gap, each vent for a torn or missing screen and each soffit joint for an opening. A high section that cannot be reached from the ground is listed as not checked.
From inside, the attic is walked on the boards with a light. A beam of light visible through a gap at the eave, or a draught moving insulation near a vent, marks a route the outside check may have missed. The route is recorded on a plan.
How are the entries sealed?
A fitted screen on a vent, a caulk or foam for a small joint and a metal cover for a larger opening are the usual methods. The material is chosen for the surface and its exposure to the weather.
A vent without its screen is the simplest repair and often the most effective. A fine mesh screen keeps the insects out while letting the vent work. A torn screen is replaced at once and noted on the list.
Foam used at a larger opening is trimmed and covered where sun reaches it, because foam breaks down under ultraviolet light. Insulation is not pushed into a gap to hide it; the gap is sealed and the insulation is put back so it covers the boards as before.
When should the work be done?
The sealing is best finished before the autumn, when the insects begin to look for overwintering spots. A check after the first heavy storm and again in the spring looks for any gap that has opened.
A storm or a freeze can move roof boards and open a gap at the eave, so a check after either is worth making. The report lists each check and its date, so the next season starts from a known condition.
A homeowner can check the attic monthly in the cool season from the hatch, noting any new insect, dropping or draught near a vent. Those notes are the most useful record for the next visit.
What a homeowner can do before the autumn
Before the autumn, a homeowner can walk the attic from the hatch, check the vents for screens and note any gap at the eave. A short list of those checks makes the attic visit faster and clearer.
A torch and a dated notebook are enough for the check. The homeowner notes each gap, each torn screen and any insect seen in the attic in the warm weeks, so the technician has a starting point.
The check is repeated after the first storm of the autumn, when a loose board or a lifted soffit is most likely to show.
