What are Some Bugs That Leave Black Spots on Walls?

There are many bugs that leave black spots on walls. Learning to tell the difference between these black spots will help you solve your pest problem.

Several insects leave distinctive marks on walls, doors, and other surfaces. Don’t ignore these black spots on the walls – they could be clues to an infestation! Knowing what to look for can help you identify the bug causing trouble in your home so you can tackle the issue effectively.

5 Bugs That Leave Black Spots on Walls

5 common bugs that leave black spots on walls

Bed Bugs

Bed bugs are small, flat insects that leave bed bug poop after feeding on the blood of humans and other animals. They leave dark blackish spots on walls, furniture, pillows, sheets, and anywhere they travel after feeding. As they move around, they will deposit black ink-like marks.

Bed bugs are one of the main culprits for bugs that leave black spots on walls. If you take a wet cotton swab and rub the site, it will smear and turn a dark rusty black. However, just because the spot smears does not mean it’s 100% from bed bugs.

A clue is where you are seeing these black spots. If you want to learn how to spot bed bugs, look for the black marks.

Are the black areas on your walls in the kitchen? Or are they on the molding behind your bed? In most cases, bed bugs will not leave their fecal stains in kitchens or bathrooms.

That Leave Black Spots on Walls

What To Do If You Think it Bed Bugs

Start doing a thorough inspection of your entire bedroom. Be sure to research how to find bed bugs during the day thoroughly.

You’ll need to check many bed bug hiding places, like behind the headboard and under the bed frame. If the black spots on your wall are from bed bugs, then you’ll probably be able to find a bug nearby.


Roaches are one of the main culprits of bugs that leave black spots on the walls of your home. These markings may indicate that roaches are setting up shop in your space. 

If they have been living in your home for a while, their droppings can accumulate in cabinets, behind light switches, under counters, bathrooms, and other places. 

Roach droppings are often grainy and sticky and come in shades of brown or black – or sometimes a combination of both. Since they are sticky, you may also find these marks on walls, moldings, and appliances.

roaches Leave Black Spots on Walls

What To Do If You Think it’s Roaches

Roaches tend to be nocturnal and come out to scavenge at nighttime. So if you suspect the black marks are from cockroaches, you can do a few things.

Firstly, set out some sticky traps near the areas where you see black spots on the walls. Secondly, get up in the middle of the night and quickly turn the lights on; you may see roaches scattering.

Just be aware that there are plenty of other bugs that look like roaches. However, cockroaches do not like the light, so they prefer to look for food when it’s dark. In contrast, beetles will be out more often in the daytime.

If you find roaches, call a pest control professional to help you strategize. You can also use some Advion roach gel bait. It’s what all of our NYC clients with a roach issue swear by.

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House Flies

Have you noticed any strange black spots appearing on your walls and windows? If so, they may not be dirt but a sign that houseflies reside in your home. 

As these pests flit indoors, they can leave behind small, dark, and grainy specks of their excrement. These black marks can appear anywhere the flies land, including your food. You should treat them as a warning sign of an infestation. 

What are Some Bugs That Leave Black Spots on Walls_ Flies

What To Do If You Think it’s House Flies

Ensure you take your garbage out regularly and use screens on your windows. These two things will significantly reduce the chance of flies laying eggs indoors. 

Fruit Flies

As far as fruit flies go, the most common ones are the dark-eyed fruit fly and the red-eyed fruit fly. The dark-eyed fruit fly is harder to control and is more likely to leave behind black fecal spots on your walls, food packages, and floors.

Anywhere these dark-eyed fruit flies land, they can leave behind black spots. These are their droppings that have a distinct odor.

Bugs That Leave Black Spots on Walls

What To Do If You Think it’s Fruit Flies

If you suspect fruit flies may cause the black marks on your wall, take preventive measures to reduce their numbers. Start by throwing away any overripe fruits and cleaning all drains. It’s also imperative to seal up any alcohol, vinegar, syrups, or other liquids that they can feast on.

These fruit flies infest bars commonly since there are plenty of beverages to feed on. So if you’ve seen any of these dark spots at the bar, it’s best to call a professional pest control service to eliminate them.


Silverfish droppings are small, dark, and like tiny peppercorns. So if you see black flakes like peppercorns around your moldings and floors, it may be silverfish droppings. However, they won’t stain the walls like roaches and bed bug feces.

silverfish Leave Black Spots on Walls

What To Do If You Think it’s Silverfish

If you suspect Silverfish, the best thing to do is to clean, vacuum, and seal up all crevices. A thorough cleaning will help eliminate them and keep them away. As with other pests, a professional exterminator can help eliminate these bugs if the problem persists.

Other Possible Causes of Black Spots on Walls


Black mold can appear on walls where there is a high humidity level. The best thing to do for black mold is to use a bleach mixture to wipe down the walls and then dehumidify the room.

You’ll need to check your exterior walls and roof to see any leaks. A dehumidifier can work wonders for reducing moisture levels in the home.


Artillery fungus can appear on your walls, especially if you have mulch or rotting wood nearby. The fungus will look like black spots on your wall.

These fungal spots are hard to remove and are more of a tar-like texture. So you’ll probably not confuse them with the black mold spores.

It’s essential to remove all rotting wood and mulch from the base of your home. The problem should correct itself by doing this and using a dehumidifier.

Final Thoughts for Bugs That Leave Black Spots on Walls

If you are wondering what kind of bugs leave black spots on walls, this article should help. More importantly, if you’ve noticed strange black marks on your walls, floors, and windows, it may indicate an infestation. Roaches, house flies, fruit flies, and Silverfish can all leave behind black marks, so it’s essential to know which type of bug is causing the issue.