Many people never see a live bed bug until the infestation is severe. And even then, they may not see a live one. In fact, I’ve heard it said that if you see just one live bed bug, you already have a runaway problem. And that’s because bed bugs are so good at hiding.

But that doesn’t mean you can’t find signs of them. For most people, the first sign of a bed bug problem are the bites on their body. We’ll get to those in the next section.

But another sign are black pepper-like dark spots and stains on the bed. They look like magic marker stains, or a series of dots from a ballpoint pen. That’s their fecal matter – in other words, your digested blood. Here’s a photo, taken by Dr. H.J. Harlan, of the Armed Forces Pest Management Board (find the original document here)

Generally, when an exterminator comes to your home to look for signs of infestation, he will check your bed for those fecal stains.

You will sometimes see flecks of dried blood on your bedsheets, which are usually very small – not much bigger than the period at the end of this sentence.

And occasionally (and most disgustingly) you will find a bug that was crushed when you rolled onto it while you were asleep. If you find one, don’t throw it down the toilet. Keep it to show to your PCO.

You might also find eggshells near the bug’s hiding places, though, as I mentioned, these can be very hard to see.