A couple posts ago, in Wood Floor Mystery #1: The Case of the Spreading Black Spots, we looked at some mysterious black crud that first showed up in the wood flooring and was taking over an entire home. I asked for your ideas, and looking back at them now, the first comment out of the chute from someone named Bert appears to be the front runner. His idea? Bed bugs. I researched the crud that bed bugs leave behind (feces and blood) and compared it to some other possibilities, mold/mildew and black rust. When I began Googling about bed bugs, I found that Long Island, N.Y., has had a serious bed bug problem for quite some time. Guess where this wood flooring nightmare is? Long Island.

A very reputable laboratory did a mold/mildew study on some samples that came up negative. My tests show it is not MPCC (Metallic Particle Corrosion Contamination) or, more simply, black rust.

So what about our reader’s assertion that this could be the result of bed bug infestation?

Tests are ongoing, as the homeowner swears there is no bed bug problem. Oddly, when posed with the bed bug hypothesis, I was met with immediate rejection, uncomfortable laughter, and what seemed to be dismissive consternation. However, this client had told me he had bedding “covered” with the same spots and he would mail it to me for testing (it never arrived). The test kits I sent at my own expense were not returned to me, either. Lastly, he told me he would know if it were bed bugs because he was extremely familiar with their presence, including the effects of bites and infestation.

My go-to “bug guy” was employed with a national extermination company and had extensive training. He told me he had to sign many confidentiality agreements when large national hotel chains (including 5-star locations) were involved when bed bug infestation was a concern. He also informed me that many states have written laws to control bed bug infestations. And in New York City, a law passed in 2010 mandates that new residential tenants in New York City be given a one-year bed bug infestation history. My bug guy offered a plausible explanation for my client’s defensive reaction to the bed-bug hypothesis and explained that it is extremely commonplace. He said anyone would be concerned and even take offense when their cleanliness and even property value may be called into question.

Compare this pic of bed bug stains I found online (from exterminator catseyepest.com) on the left with our pic from this case (where the spots had spread to a leather sofa) on the right:

Seeing that tests are now on hold and all communication has ceased (maybe because of the holidays?) and no insect inspections have been performed, this mystery is moving to the back burner while we move on to Wood Floor Mystery #2: The Topcoat That Wouldn’t Stick. Stay tuned!


Stephen Diggins works for Wood Pro Inc. in their Salem, N.H., branch as manager and training director. He has many years of installation, sanding, finishing, gymnasium design and technical consulting experience, which he uses to assist his flooring customers on a regular basis. With almost 30 years in the flooring industry, he has been a freelance columnist for magazine, newsprint and online medias and has conducted product seminars ranging from wood flooring to luxury vinyl tile.