Module 1 of 7 · about 5 minutes
What bed bugs look like at each stage, the signs they leave behind, and where to look first.
Reviewed by the ThermoPest technical team · Last reviewed October 2026
Adult bed bugs are flat, oval, reddish-brown insects about 5mm long, roughly the size of an apple seed. More often than the insects themselves, you'll see the signs they leave: small dark spots on mattress seams and bed frames, tiny blood smears on sheets, and pale shed skins. They usually hide close to where people sleep or rest.
Life stages, roughly to scale
Hard to see without a torch. Signs are usually easier to spot than the insects themselves.
Mattress seams and piping, bed frame joints, headboards, bedside furniture, skirting boards near the bed, sofa seams and cushions, and behind loose wallpaper or pictures. Wherever someone sleeps on a sofa or chair, check there first.
Where to look first
Mattress seams and piping
Bed frame joints
Headboard and the wall behind
Bedside furniture
Skirting boards near the bed
Someone sleeping on a sofa or chair? Check there first.
Carpet beetle larvae, fleas and spider beetles are often mistaken for bed bugs. If you’re unsure, photograph it (with something for scale) and report it. A pest professional can confirm. Don’t try to identify by bites alone; Module 2 explains why.
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