Found Mud Tubes Full of Spiders on Curtains? Mason Wasp and Mud-Dauber-Type Nests Explained
Small clay-like tubes on curtains, window frames or walls with spiders inside are usually not a hornet nest. They are more consistent with a solitary mud-building wasp nest, often called a mason wasp or mud-dauber-type nest.
This Bon Accord Pest Control guide explains why the spiders are inside, how an open window can allow this to happen in a flat, whether the wasp is dangerous, and what to do safely before spraying or removing anything.
Quick answer: what are mud tubes full of spiders?
If you have found small mud tubes or clay-like cells on curtains, window frames, walls, blinds, furniture, a balcony door or inside a flat, and the broken cells contain spiders and pale larvae, it is most likely a solitary mud-building wasp nest.
People often call these mason wasp nests, mud dauber nests, mud wasp nests or potter wasp nests, although the exact species cannot be confirmed from photos alone. The important point is that this is usually not a hornet nest and not a normal social wasp nest.
Simple explanation: a female solitary wasp builds mud cells, catches spiders, places them inside as food for the young, lays an egg and seals the chamber. It looks unpleasant indoors, but it is normally much lower risk than an active wasp or hornet colony.
In a recent Bon Accord Pest Control case, a London client found mud-like tubes attached to the living-room curtains after leaving a window open. When the tubes were broken, they contained several spiders and developing larvae. This is a classic sign of a solitary mud-building wasp using the curtain folds as a sheltered nesting location.
Real London case: mud cells found on living-room curtains
A client contacted Bon Accord Pest Control after discovering strange mud tubes attached to the curtains in her living room. The window had been left open, and the tubes appeared on the curtain folds near the window area.
When the mud was opened, it contained:
- several small spiders
- pale larvae or grub-like stages
- dry mud or clay-like chambers
- individual sealed cells rather than one large paper nest
- no large number of flying wasps inside the room
- no hornet-style paper nest
- no steady stream of wasps entering a roof, loft or wall cavity
This combination is highly suggestive of a solitary mud-building wasp, not a hornet colony. The most important clue is the spiders inside the mud cells. Many solitary wasps use insects or spiders as food for their larvae, and some species paralyse spider prey before sealing it inside a nest chamber.
From photos alone, it is safer to describe this as a mason wasp / mud-dauber-type solitary wasp nest rather than claiming one exact species. That keeps the report accurate and avoids over-identification.
What are these mud tubes?
The mud tubes are usually brood cells. A female solitary wasp collects mud or clay, builds a small cell, hunts prey, lays an egg, and seals the cell.
Each sealed cell can contain one developing wasp egg or larva and several spiders or other prey items. The mud cap protects the chamber while the larva develops inside.
These cells may be built in sheltered places such as curtain folds, window recesses, behind blinds, door frames, balconies, cracks and crevices, wall corners, roof edges, sheds, garages, lofts, unused rooms, under furniture, around vents or sheltered external brickwork.
Important: these mud cells are not droppings, not cockroach egg cases and not a sign that spiders built a nest in the curtain. The spiders were placed there by the wasp as larval food.
Why are there spiders inside?
The spiders are not building the mud tubes. The spiders are food for the wasp larva.
The usual process is simple but surprising:
- A female solitary wasp finds a sheltered location.
- She collects mud and builds a small cell.
- She hunts spiders.
- She stings and paralyses them.
- She places the spiders inside the cell.
- She lays an egg.
- She seals the mud cell.
- The larva hatches and feeds on the stored spiders.
This is unpleasant to find indoors, especially on curtains, but it is normal behaviour for some solitary wasps. The spiders may look dead, but they may originally have been paralysed rather than killed immediately. This helps preserve them as fresh food for the developing larva.
For a customer, the key reassurance is that this does not mean the home is dirty and does not automatically mean there is a serious spider infestation. It usually means a solitary wasp found a quiet, sheltered location and completed part of its nesting cycle before anyone noticed.
Did leaving the window open allow this to happen?
Yes, that is very possible.
A solitary wasp can enter through an open window or balcony door, especially during warm weather. If the room is quiet, the curtains are undisturbed, and the window area provides shelter, the wasp may treat the curtain folds or window recess as a suitable nesting site.
This is more likely when windows are left open for long periods, curtains are not moved regularly, the room is quiet or unused, there is a garden, balcony, roof terrace or green space nearby, spiders are available around the building, the weather is warm, and there is access to mud, soil or damp material outside.
Client-friendly explanation: leaving a window open does not usually cause a major infestation, but it can allow insects to enter. In rare cases, a solitary mud-building wasp may build small cells indoors before the customer notices.
Is this a hornet nest?
In this type of case, it is very unlikely to be a hornet nest.
Hornets and common social wasps do not normally build small mud tubes on curtains packed with spiders. Social wasp and hornet nests are usually made from a paper-like material produced from chewed wood fibres, not from separate mud cells.
A social wasp or hornet nest is usually recognised by a steady flow of insects flying to and from a nest entrance, often around a loft, roofline, wall cavity, shed, chimney, tree hollow or ground cavity. A mud nest on curtains with spiders inside points in a different direction: a solitary wasp nest, not a large defensive colony.
Mason wasp, mud dauber, potter wasp or hornet: what is the difference?
| Feature | Mason / mud-dauber-type solitary wasp | Common wasp nest | Hornet nest |
|---|---|---|---|
| Nest material | Mud, clay or mud-like cells. | Paper-like chewed wood pulp. | Paper-like chewed wood pulp. |
| Nest shape | Small tubes or individual cells. | Round or oval nest with comb inside. | Larger paper nest, often in a cavity or sheltered place. |
| Typical contents | Spiders or other prey plus a larva or egg. | Many workers, larvae, eggs and comb. | Hornet colony, larvae and comb. |
| Typical location | Curtains, cracks, keyholes, window areas, sheds, garages, sheltered brickwork. | Loft, shed, wall cavity, roofline, ground cavity or void. | Loft, chimney, tree hollow, roof void, wall cavity or outbuilding. |
| Behaviour | Usually solitary. No large worker colony. | Social colony with workers defending nest. | Social colony with larger workers defending nest. |
| Risk level | Usually low, but can sting if trapped, crushed or handled. | Higher if active nest is disturbed. | Higher if active nest is disturbed. |
| Main clue | Mud cells full of spiders. | Steady traffic of wasps to and from one entrance. | Larger insects and paper nest activity. |
| Usual response | Identification first; safe removal if inactive; avoid unnecessary spraying. | Professional treatment usually recommended for active nests near people. | Professional advice strongly recommended. |
Is a mason or mud-dauber-type wasp dangerous?
Usually, the danger is low, especially compared with an active common wasp or hornet nest.
Solitary wasps do not have a large worker colony to defend. They are generally focused on nest building, hunting prey and laying eggs. That is why many solitary wasp situations are much less aggressive than a social wasp colony.
However, this does not mean you should handle them casually. A solitary wasp may sting if it is trapped against skin, grabbed, crushed in clothing or curtains, or disturbed while the adult is present. Any customer with a known wasp-sting allergy should avoid handling the nest and seek professional advice.
Honest risk advice: low risk does not mean zero risk. Do not touch it with bare hands. Do not crush insects in curtains. Do not let children or pets play with the mud cells. If there is active insect movement or allergy risk, ask for professional identification and removal.
Are the spiders dangerous?
The spiders inside the mud cells are usually prey collected by the wasp. In most UK domestic cases, the spiders are not the main danger. The unpleasant part is the shock of finding them inside curtains or indoors.
Some may be dead, some may be dried out, and some may originally have been paralysed. The safest approach is not to handle the spiders or nest material directly. Wear gloves, avoid breathing dust from broken material, place debris into a sealed bag, and clean the surface afterwards.
Is this a sign of a bigger infestation?
Usually, no.
A mud tube full of spiders on a curtain does not automatically mean the property has a major pest infestation. It usually means one female solitary wasp found a sheltered place and built cells.
However, it may suggest that windows are being left open without screens, insects can easily enter the flat, curtains or window recesses are not being checked regularly, there are spiders around the window or balcony area, there is suitable soil or mud outside, or the room has been quiet enough for the wasp to build undisturbed.
It is an insect access and identification issue, not necessarily a full infestation.
Why would a wasp choose curtains?
Curtains can be attractive to a solitary wasp because they provide folds, hidden spaces, shelter from rain and wind, warmth from sunlight, access near an open window and quiet surfaces that are not disturbed every day.
From the wasp’s point of view, a curtain fold near an open window may look like a protected cavity. This is why the client’s detail — the window was left open — is important.
What should you do if you find mud tubes on curtains?
Do not panic, but do not smash everything immediately. A calm, evidence-based response is best.
1. Step back
Inspect from a distance. Check whether any flying insects are present or actively entering and leaving the mud cells.
2. Take clear photos
Photograph the whole curtain, the close-up mud cells, any broken chambers, spiders, larvae and any adult insect nearby.
3. Do not spray curtains
Curtains and soft furnishings can absorb chemicals. Avoid unnecessary insecticide unless a professional has assessed the situation.
4. Keep people away
Keep children and pets away so nobody touches broken mud cells, spiders, larvae or a possible adult wasp.
5. Remove only if inactive
If small, inactive and accessible, careful physical removal may be enough. Use gloves, a scraper or stiff card and a sealed bag.
6. Call if unsure
If there is activity, allergy risk, commercial sensitivity or uncertainty, professional identification and removal is safer.
Should you spray a mason wasp or mud-dauber-type nest?
Not usually as the first step.
These nests are often small, localised and not aggressive. If the wasp has gone and the cells are inactive, physical removal and cleaning may be enough.
Spraying may be considered only where an adult wasp is present and cannot be safely excluded, there is repeated activity indoors, the customer has a high-risk allergy situation, the nest is in a sensitive place, identification confirms treatment is appropriate, or there is a wider wasp issue around the property.
Responsible pest control: not every insect requires insecticide. The correct first step is identification, risk assessment and practical advice.
How Bon Accord Pest Control would handle this type of call
For a case like mud tubes on curtains, Bon Accord would usually treat it as an identification and risk-assessment issue first.
A professional approach may include reviewing photos before attendance, checking whether the nest is active or inactive, confirming whether it looks like solitary mud cells rather than a hornet or social wasp nest, inspecting the window and curtain area, checking whether insects are still entering from outside, removing accessible inactive mud cells if appropriate, advising on safe cleaning, and giving prevention advice around open windows and fly screens.
Found strange mud tubes or a possible wasp nest?
Send clear photos through our contact page and include where the nest was found, whether insects are still active, and whether windows were left open.
Send photosCall 020 3369 6965When should you call pest control?
Call professional pest control if you are not sure what the nest is, the nest is active, wasps are still entering the room, there are several mud nests in different areas, someone in the home has a sting allergy, the nest is in a child’s room or nursery, the nest is in a commercial premises, the nest is in a hotel, serviced apartment or rental property, the customer is too worried to remove it safely, there may also be a normal wasp nest nearby, or you need written confirmation for a landlord, tenant or managing agent.
For London homes, flats and managed buildings, photo identification is often the best first step. Send clear photos through /contact-us/ and include where the nest was found, whether insects are still active, and whether any windows were left open.
What if this happens in a rental property?
If a tenant finds mud tubes on curtains, the first step is documentation. The tenant should take photos before disturbing the nest, tell the landlord or managing agent, explain whether windows were left open, note if any insects are still active, avoid spraying chemicals onto curtains, and ask for identification if unsure.
The landlord or managing agent may need to arrange professional advice if the tenant is worried, the nest is active, or the property is furnished and the curtains belong to the landlord. This is especially important in serviced apartments, HMOs, hotels and short-let properties, where a guest may panic and assume the property has hornets or a dangerous infestation.
What if this happens in a hotel, Airbnb or serviced apartment?
For hospitality and short-let properties, the issue is not only biological risk. It is also a guest confidence issue.
A guest finding mud tubes full of spiders on curtains may think the room is dirty, there is a wasp nest, there are hornets, there is a spider infestation, the property is unsafe or pest control has been neglected. The right response is fast, calm and evidence-based.
Hotel, Airbnb and serviced-apartment managers should photograph the issue, remove the room from use if the guest is distressed, arrange inspection or identification, remove the mud cells safely, check window seals, curtains and balcony doors, consider fly screens where practical, and give staff a simple explanation so they do not mislabel it as a hornet nest.
How to prevent this happening again
You cannot stop every insect from entering a home, but you can reduce the risk.
Keep windows managed during warm weather
- Avoid leaving windows wide open all day when nobody is home.
- Use trickle ventilation where appropriate.
- Close windows when the room is unused for long periods.
- Pay attention to balcony doors and garden-facing windows.
Install insect screens where practical
Fly screens are very useful for ground-floor flats, garden-facing rooms, bedrooms, kitchens, balcony doors, homes near parks or gardens, and clients who like sleeping with windows open.
Move curtains regularly
- Open and close curtains daily.
- Check folds near open windows.
- Inspect behind heavy curtains.
- Vacuum around window recesses.
Reduce indoor attraction to insects
- Avoid leaving lights on beside open windows at night.
- Clean window ledges.
- Remove dead insects from sills.
- Keep balcony areas tidy.
- Manage spider webs around window frames.
Check quiet rooms
Mud cells are more likely to go unnoticed in guest bedrooms, spare rooms, living rooms used only occasionally, storage rooms, second homes and serviced apartments between bookings.
Is this related to poor hygiene?
No, not usually.
A mud-building solitary wasp nest on curtains is not the same as cockroaches, mice, bed bugs or flies linked with hygiene, food sources or structural access. It can happen in a clean flat if the window was open, the wasp found a quiet place, spiders were available nearby, the curtain folds offered shelter and the nest was not noticed immediately.
Clients should not be embarrassed. It is unusual, but it can happen.
Does this mean the flat has too many spiders?
Not necessarily.
The wasp may have collected spiders from outdoors, around window areas, from balcony corners or from nearby building surfaces. But if there are many spider webs around the window, balcony or curtain area, it is worth cleaning them down and reducing insect harbourage around the frame.
Spiders themselves are usually not a serious pest in UK homes, but webs, insects and open windows can make a window area more attractive to other insects.
Safe cleaning after removal
After removing inactive mud cells, wear disposable gloves, place mud, spiders and larvae into a sealed bag, vacuum loose debris carefully, wipe hard surfaces with normal household cleaner, and follow the fabric care label for curtains. If the curtain is delicate or stained, consider professional cleaning.
Do not use strong insecticide sprays on soft furnishings unless professionally advised. If larvae or spider remains have dropped onto carpet or flooring, vacuum thoroughly and dispose of the vacuum contents safely.
Common mistakes to avoid
- Calling it a hornet nest without evidence.
- Spraying curtains heavily with insecticide.
- Crushing insects with bare hands.
- Letting children touch the mud cells.
- Assuming the property has a major infestation.
- Ignoring active flying insects.
- Removing the nest without photos.
- Failing to check whether the window is still allowing access.
- Throwing away evidence before identification.
- Using online images to guess the exact species too confidently.
The professional wording should be careful: “This appears consistent with a mason wasp or mud-dauber-type solitary wasp nest, but exact species identification from photos alone is not guaranteed.”
Why this is not the same as a normal wasp nest
A normal social wasp nest is a colony issue. It may involve many wasps, a queen, workers, brood comb, repeated traffic and defensive behaviour.
A mud-cell nest on curtains is usually a solitary female’s brood chamber. It is not normally a swarm, colony or large nest. This is why correct identification matters: a small solitary wasp mud nest and an active social wasp colony require very different responses.
Client-friendly explanation Bon Accord can send
Thank you for sending the photos. Based on the images, this does not look like a hornet nest or a large social wasp colony. It appears more consistent with a small solitary mud-building wasp nest, often described as a mason wasp or mud-dauber-type nest. These wasps can build small mud cells in sheltered places, and the spiders inside are usually placed there as food for the developing larvae.
This can happen if a wasp enters through an open window and finds a quiet, protected area such as curtain folds. It is unpleasant to find indoors, but it is usually much lower risk than an active wasp or hornet nest. We would recommend avoiding direct handling, keeping children and pets away from the area, and arranging safe removal or identification if there is still activity.
Bon Accord Pest Control advice
If you have found mud tubes, strange insect cells, spiders inside a nest, or something that looks like a wasp or hornet nest in your home or flat, do not guess.
Bon Accord Pest Control can help identify the issue from clear photos and advise whether it needs removal, monitoring, cleaning or treatment.
This is especially useful for London flats, rental properties, furnished apartments, HMOs, hotels, serviced apartments, homes with children or pets, clients with sting allergies, and situations where the insect may be confused with hornets or wasps.
Need insect or wasp nest identification in London?
Send clear photos through our contact page or call Bon Accord Pest Control for advice.
Contact Bon AccordCall 020 3369 6965Useful references for this identification article
FAQ: Mud tubes full of spiders on curtains
What are mud tubes full of spiders?
They are usually mud cells built by a solitary mud-building wasp. The spiders are placed inside as food for the developing wasp larva.
Are mud tubes full of spiders a hornet nest?
Usually not. Hornet nests are normally paper-like colony nests, not small mud cells packed with spiders.
Why are spiders inside the mud nest?
Some solitary wasps hunt spiders, paralyse them, place them inside a mud cell, lay an egg and seal the chamber. The larva then feeds on the spiders.
Can a wasp build a nest on curtains?
Yes, it can happen. A solitary wasp may enter through an open window and build mud cells in curtain folds if the area is quiet and sheltered.
Is a mason wasp nest dangerous?
Usually the risk is low, but the wasp can still sting if trapped, crushed or handled. Avoid touching it with bare hands.
Are mud dauber wasps aggressive?
Mud-dauber-type solitary wasps are generally much less aggressive than social wasps because they do not have a large colony to defend.
Should I spray a mud nest on curtains?
Not usually. Avoid spraying curtains with insecticide unless a professional has assessed the situation. If inactive, safe physical removal and cleaning may be enough.
What should I do if I find mud cells on curtains?
Take photos, keep children and pets away, check for adult wasp activity, avoid spraying, and arrange professional identification if unsure.
Are the spiders alive?
They may originally have been paralysed by the wasp. By the time the nest is discovered, some may be dead or dried out.
Does this mean my home is dirty?
No. This can happen in a clean flat if a solitary wasp enters through an open window and finds a quiet, sheltered place to build.
Does it mean I have a spider infestation?
Not necessarily. The wasp may have collected spiders from outdoors or around the window area. However, it is worth cleaning webs and checking window recesses.
Can this happen in London flats?
Yes. It is unusual, but it can happen in London flats, especially near open windows, balconies, gardens, roof terraces or green spaces.
Should landlords deal with this?
If the property is rented or furnished, the tenant should report it with photos. The landlord or managing agent may need to arrange identification or safe removal if the nest is active or the tenant is worried.
Can this happen in hotels or serviced apartments?
Yes. It is rare, but possible if windows are left open and curtains remain undisturbed. Fast identification is important so it is not wrongly treated as a hornet nest.
How do I prevent it happening again?
Use fly screens where practical, avoid leaving windows wide open for long periods, move curtains regularly, check window recesses and reduce insects and webs around frames.
Can Bon Accord identify this from photos?
Yes. Send clear photos of the mud tubes, the location, any insects nearby, and the contents of broken cells through /contact-us/.
