Quick Answer: Adult bed bugs are apple-seed sized (4 to 5mm), flat, oval, and reddish-brown. On your mattress, look for rust-brown excrement stains, tiny blood smears, pale yellow shed skins, and the bugs themselves hiding in seams, tags, and folds. Nymphs are smaller and nearly translucent. Eggs are 1mm, pearl-white, and very hard to see without magnification.
In This Guide
Reading Time: About 7 minutes
What Adult Bed Bugs Look Like
Adult bed bugs (Cimex lectularius) are small insects that are visible to the naked eye, though only just. Here are their key characteristics:
Size: Adults measure roughly 4 to 5 millimetres in length, about the size of an apple seed. They are not microscopic, but they are small enough to miss if you are not looking carefully.
Shape: Flat and oval when not recently fed. After a blood meal, they become more cylindrical and slightly elongated as their abdomen fills. The flattened shape when hungry allows them to hide in very thin gaps and crevices.
Colour: Mahogany or reddish-brown when unfed. After feeding, they become darker and redder as blood fills their abdomen. The colour shift is one reason unfed bugs can be harder to spot, as the mahogany colour blends with darker fabrics.
Appearance: They have six legs, short antennae, and no wings. Despite looking wing-like, their thorax does have vestigial wing pads, but bed bugs cannot fly. They move by crawling, though they can move relatively quickly across surfaces.
Under good lighting with reading glasses or a magnifying glass, adult bed bugs are distinctive enough to identify once you know what you are looking for. The challenge is finding them, not recognising them once spotted.
Nymphs and Eggs
Bed bugs go through five nymph stages before reaching adulthood. Each stage requires a blood meal to progress to the next.
First instar nymphs (just hatched): Approximately 1.5mm long, translucent or pale whitish-yellow. Extremely difficult to see without magnification. They become reddish when recently fed, which is often the only time they are visible to the naked eye.
Later instar nymphs: Gradually darken and grow with each moult, progressing through the stages toward the adult mahogany colouration. Second and third instar nymphs are still very small (2 to 3mm) and semi-translucent.
Eggs: About 1mm long, pearl-white to cream coloured, and barrel-shaped. They are laid in clusters of 1 to 5 in sheltered locations and are sticky when first deposited, allowing them to adhere to surfaces. They are extremely difficult to see with the naked eye. A female bed bug lays 1 to 5 eggs per day and 200 to 500 eggs over a lifetime.
Life Cycle and Timing
Bed bug eggs hatch in 6 to 10 days at room temperature. Nymphs develop to adulthood in 5 to 6 weeks under warm conditions with access to blood meals. Adults can live 6 to 12 months. In cold conditions, development slows significantly and adults can survive extended periods without feeding, sometimes over a year.
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Signs to Look For on Your Mattress
Even if you do not see a live bed bug immediately, the signs of their presence are often visible on your mattress:
Rust-brown or dark staining: Bed bug excrement (faeces) appears as small dark spots or staining, similar in appearance to felt-tip pen marks. These stains are often clustered in areas where bugs congregate. On light-coloured mattress fabric, they appear as dark rust or brown smears or dots. They do not wipe off easily because they are partially absorbed into fabric.
Blood smears: Small reddish-brown smears or spots can appear when a feeding bug is accidentally crushed as you shift in sleep. These look like small blood stains, typically 1 to 3mm across.
Pale yellow shed skins (cast exoskeletons): Nymphs shed their skin (exoskeleton) at each stage of development, leaving behind pale yellow translucent shells. These are visible in hiding areas and are a clear sign of an active population because they accumulate over time. They look like hollow, papery insect shells.
A musty odour: Heavy infestations sometimes produce a sweet, musty odour described as similar to coriander or a damp towel. This is caused by pheromones released by the bugs. Mild infestations typically do not produce a detectable smell.
Live bugs: If the infestation is established, you may see live bugs in mattress seams and folds, particularly if you pull back the mattress cover and look carefully with a flashlight.
Distinguishing Bed Bug Stains From Other Mattress Stains
Bed bug excrement stains are typically very small (1 to 3mm), clustered, and dark rust-brown to black. They appear concentrated in areas where bugs hide (seams, folds) rather than spread uniformly. Sweat stains tend to be larger, yellowish, and distributed across the sleep surface. Coffee or drink stains are typically in isolated spots. Blood smears from bed bugs are small and often at seam edges.
Where to Look on a Mattress
Bed bugs are attracted to warmth and carbon dioxide from sleeping humans. They hide close to their food source but out of direct light. On a mattress, the most common hiding locations are:
Mattress seams and piping: The most common location. Bed bugs hide in the folded fabric at the edges of the mattress, using the tight seam as shelter. Check both the top and bottom seams all the way around the perimeter.
Tags and labels: The fold of fabric under mattress tags creates a sheltered spot. Lift the tags and examine underneath with a flashlight.
Corner handles: If your mattress has fabric handles for turning, check the folds and attached areas underneath the handles.
Box spring: The box spring is often more heavily infested than the mattress itself because the frame interior provides more shelter. Check the fabric covering the underside of the box spring as well as the wood frame and corner joints.
Underneath the mattress: Check the underside of the mattress along seams. If you lift the mattress off the foundation, also check the surface of the foundation.
Insects Commonly Confused With Bed Bugs
Several common household insects are mistaken for bed bugs, which matters because misidentification leads to incorrect treatment.
| Insect | Size | Colour | Key Difference |
|---|---|---|---|
| Bed Bug (adult) | 4 to 5mm | Reddish-brown | Flat oval, no wings, found in mattress seams |
| Carpet Beetle (larva) | 4 to 5mm | Brown/tan with bristles | Has visible bristles/hairs, more elongated |
| Spider Beetle | 1.5 to 4mm | Reddish-brown to dark brown | Rounded body, spider-like legs, longer antennae |
| Bat Bug | 3 to 5mm | Light brown | Nearly identical to bed bug; requires microscope to distinguish |
| Booklouse | 1 to 2mm | Pale/translucent | Much smaller, does not bite, found in humid areas |
If you are uncertain about identification, collecting a specimen in a sealed container and taking it to a licensed pest control company or your local public health unit for identification is the most reliable approach.
What to Do if You Find Them
It is important to be clear on this point: mattress cleaning, vacuuming, or DIY treatments do not eliminate a bed bug infestation. Bed bugs hide in many locations beyond the mattress, including wall voids, electrical outlets, picture frames, nightstands, and furniture. Treating only the mattress leaves populations in all other locations intact.
If you identify bed bugs, the appropriate response is:
Contact a licensed pest management professional. In Ontario, pest control professionals must be licensed under the Pesticides Act. A professional assessment will determine the extent of the infestation and the appropriate treatment protocol (heat treatment, chemical treatment, or a combination).
Do not move furniture or mattresses to other rooms, as this can spread the infestation. Do not throw out your mattress immediately -- in most cases, a mattress can be treated and encased. Throwing it out without treatment often spreads bugs to other areas of your home or building.
Following extermination, a mattress encasement (see our article on mattress covers vs pads) should be applied to trap any surviving bugs and prevent reinfestation of the mattress surface.
After Extermination: Replacing Your Mattress
In some cases, particularly severe or long-term infestations, a mattress replacement may be recommended by your pest control professional after successful extermination. If that applies to you, Mattress Miracle in Brantford can help you select a new mattress and pair it with a quality encasement for protection. Our team does not work on commission, so you will get straightforward advice on what you need without upselling.
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Call 519-770-0001Frequently Asked Questions
Can you see bed bugs with the naked eye?
Yes, adult bed bugs are visible to the naked eye. At 4 to 5mm they are small but noticeable once you know what to look for, particularly against light-coloured fabric. Nymphs in early stages and eggs are much harder to see without a magnifying glass.
Do bed bugs stay on the mattress during the day?
Bed bugs typically retreat from the sleeping surface during the day to hide in protected harborage areas. While the mattress seams are a common hiding spot, they also hide in box springs, bed frames, headboards, nightstands, baseboards, and any crack or crevice near the bed. They emerge primarily at night to feed.
What does a bed bug bite look like?
Bed bug bites typically appear as small, raised red welts that may be itchy. They are often arranged in a line or cluster (sometimes called "breakfast, lunch, and dinner" groupings). However, up to 30 percent of people do not react visibly to bed bug bites, and bite appearance varies considerably between individuals. Bites alone cannot confirm bed bugs, as they look like many other insect bites. Look for physical evidence on the mattress.
Can cleaning your mattress get rid of bed bugs?
No. Cleaning your mattress, including vacuuming and spot treatment, does not eliminate a bed bug infestation. Bed bugs hide throughout the room, not just on the mattress surface. Professional extermination is required. An encasement can be used after treatment to trap any remaining bugs in the mattress, but it is not a standalone treatment.
What are the best mattress covers for bed bugs, and how do I choose the right encasement in Canada?
Mattress covers for bed bugs are specifically designed encasements - different from standard waterproof protectors - that fully zip around all six sides of the mattress with a bite-proof, pore-free barrier.
An effective bed bug mattress encasement must meet three criteria: a zipper with a welded end seal (standard zipper teeth leave gaps large enough for bed bugs to pass through), a fabric with pore size small enough to trap existing bed bugs inside while preventing entry of new ones (lab-tested encasements specify pore size below 0.6 millimetres, which is smaller than a first-instar bed bug nymph), and a material that is durable enough to hold up to 18 months of encasement without tearing - because bed bugs inside the encasement die of starvation on average within 12 to 18 months.
In Canada, recommended bed bug encasements are available from SafeRest (Amazon Canada, $65 to $95 for queen), Protect-A-Bed AllerZip (HomeSense, specialty retailers, $89 to $130), and BedBug.com (ships to Canada, $79 to $119). A standard mattress protector - even a fully waterproof one - is not a bed bug encasement: it covers only the top and sides without a sealed zipper.
Health Canada recommends mattress encasements as a front-line component of an integrated bed bug management plan when an infestation is confirmed.
Talia says: "If you are dealing with bed bugs, encasements on both the mattress and box spring are non-negotiable. A $90 encasement saves a $1,200 mattress - it is one of the clearest value decisions in our category." Browse our mattress protectors collection for bed bug encasements and allergen-rated covers.
Sources
- Public Health Ontario. "Bed Bugs: Public Health Significance and Control." publichealthontario.ca, 2023.
- Centers for Disease Control and Prevention. "Bed Bugs FAQs." cdc.gov, 2022.
- Entomological Society of Canada. "Bed Bug Identification Guide." esc-sec.ca, 2022.
- Ontario Ministry of the Environment. "Bed Bug Regulation and Pesticide Use." ontario.ca, 2023.
- Potter MF. "Bed Bugs." University of Kentucky College of Agriculture Entomology Extension. uky.edu, 2023.
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If you have gone through an extermination process and need to replace your mattress, or want to protect a treated mattress with a proper encasement, come in and we will help you find the right solution.