Since bed bugs feed on blood, they leave behind small brown stain spots in their feces. These can remain long after the insects have been eliminated. The stains are protein-based, since they are essentially made of blood, and require a more aggressive removal approach than many other types of stains.
Bed Bug Shape. Unfed bed bugs are flat and broad-oval. Fed bed bugs become swollen and more elongated. Bed Bug Size. Adult bed bugs can reach a size of about 1/4 inch long. Nymphs range from 1.3 mm to 4-5 mm. Bed Bug Life Cycle. Bed bug biology naturally promotes infestation.
Dark spots (about this size: •), which are bed bug excrement and may bleed on the fabric like a marker would. Eggs and eggshells, which are tiny (about 1mm) and pale yellow skins that nymphs shed as they grow larger.
Blood stains, bed bug stains, and fecal matter stains all have one thing in common: they're all organic. Cold water loosens the organic matter so it doesn't set in the fabric. Warm water, on the other hand, will set bed bug stains.
They live off of the blood in animals and humans. Look around the edges of your mattress, the creases of your sheets, and pillowcases. If there is a bedbug problem, you will see a mass of small black bugs ranging from eggs (1mm) to adults (5mm, size of an appleseed).
Blood Smears and Fecal Stains. Smears of blood on sheets are one of the early warning signs that bed bugs might be sharing your bed. Stains like the ones in the picture below happen when recently fed bugs get squashed in the bed by a person moving unexpectedly.