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Overwintering Insects: The Hidden Pests
Already Living in Your Walls (Boxelder
Bugs, Stink Bugs & More)
As the cold Wisconsin weather rolls in, many homeowners breathe a sigh of relief, believing the
pest problems of summer and fall are finally over. Unfortunately… that’s not always true.
Some pests don’t just disappear for the winter — they move into your home and wait until
spring.
These insects are known as overwintering pests, and if you’ve ever noticed bugs suddenly
appearing in your house during the first warm days of late winter or early spring, you’ve likely
experienced them firsthand.
At Nexus Pest Solutions, we help clients across Southeast Wisconsin manage these sneaky
seasonal invaders. Here’s what every homeowner needs to know.
🐞 What Are Overwintering Pests?
Overwintering pests are insects that avoid freezing temperatures by hiding inside sheltered
areas — including:
● Wall voids
● Attics
● Basements
● Gaps behind siding
● Window and door frames
● Garages and storage areas
They don’t usually feed or reproduce in winter. They simply sleep, hide, and wait — often in
large numbers.
When the sun warms certain parts of the home (like south-facing walls), these insects “wake up”
and end up inside your living space.
🚨 Common Overwintering Pests in Wisconsin
Here are the top offenders Nexus handles every November and December:
1. Boxelder Bugs
Easily recognized by their black bodies and red lines, boxelder bugs gather in massive groups
on sunny siding in fall.
Once temperatures drop, they slip into tiny gaps around:
● Siding
● Rooflines
● Windows
● Vents
They’re harmless but extremely annoying, and they stain walls and fabrics when crushed.
2. Stink Bugs
These shield-shaped insects release a foul odor when threatened — hence the name.
They crawl into homes every fall and emerge during the warmest parts of winter.
They’re famous for:
● Buzzing around lights
● Appearing on curtains and windows
● Creating an unpleasant smell when touched or vacuumed incorrectly
3. Asian Beetles (Ladybug Look-Alikes)
Often confused with harmless native ladybugs, Asian beetles gather by the thousands in warm
corners of siding and sneak indoors.
Once inside, they:
● Cluster in groups
● Leave yellow stains
● Emit a pungent “musty” odor
● Show up on ceilings and around windows
4. Cluster Flies
Cluster flies overwinter in huge numbers in attics and wall voids.
They move slowly but can fill rooms with dozens of flies on warm winter days.
They also leave behind:
● Droppings
● Wing marks on windows
● Odors in poorly ventilated areas
5. Brown Marmorated Stink Bugs
A newer invasive species in Wisconsin. These can cause:
● Electrical damage in attics (from clustering near outlets or warm appliances)
● Persistent winter activity
● Strong odors if disturbed
🔍 Why They Choose Your Home
Overwintering pests don’t enter by accident. They’re specifically searching for:
Warmth
Even a few degrees of heat leaking through siding will attract them.
Micro-Gaps
Openings as small as 1–2 millimeters allow them inside, such as:
● Unsealed trim
● Loose siding
● Cracked window caulk
● Gaps around exterior light fixtures
● Attic vent screens
Sun-Facing Surfaces
South or southwest walls warm up quickly, drawing huge swarms.
🛑 Why DIY Methods Usually Don’t Work
Sprays and “bug bombs” are ineffective because overwintering pests are hiding deep inside
inaccessible areas:
● Wall voids
● Rafters
● Behind insulation
● Behind soffits and eaves
● Between siding layers
Once they’re in, only professional-grade exclusion and exterior treatments work.
️ How to Prevent Overwintering Insects
The best time to prevent these insects is before they enter — but if they’re already inside, you
still have effective options.
Fall Prevention (Prep for Next Year)
● Seal exterior cracks and crevices
● Replace worn weather stripping
● Repair screens on attic vents and windows
● Tighten loose siding
● Use professional-grade perimeter treatments
Winter Management (For Right Now)
Once they’re already inside, Nexus can:
● Identify the primary entry points
● Apply targeted attic and wall-void treatments
● Seal gaps along windows, soffits, and door frames
● Remove clusters safely without spreading odors
● Apply safe residual treatments that stop new activity
Most homeowners are shocked by how many insects we remove — and how many were hiding
all along.
🧼 What NOT to Do
Avoid these common mistakes:
● Do not crush stink bugs or Asian beetles — they stain and smell
● Avoid overusing indoor sprays — these rarely reach the insects
● Don’t vacuum stink bugs with a bagless vacuum — the smell lingers for months
● Don’t ignore recurring winter sightings — that means there are many more hidden
🏡 Professional Winter Overwintering Treatment
Nexus Pest Solutions offers:
● Exterior sealing
● Attic treatments
● Wall-void dusting
● Prevention barrier sprays
● Indoor removal and cleanup
● Recommendations for long-term exclusion
Plus, everything we do is backed by our money-back guarantee, giving you total peace of
mind.
📞 Ready to Evict Your Hidden Winter Guests?
If you’re seeing strange bugs in your home during December or noticing them reappearing on
warm winter days, it’s time for a professional inspection.
Nexus Pest Solutions
📍 11512 N Port Washington Rd, STE 206, Mequon, WI 53092
📞 (414) 355-3732
💻 Online booking available 24/7
️ Backed by our Money-Back Guarantee
