I recently found an apartment that had American spider beetles in the bathroom, which the resident mistook as bedbugs. I mistakenly thought it was a flea except for the red, smooth shininess of its abdomen. My questions are where does the beetle come from this time of the year, what is its biology, and is this a blood feeding pest?
Well, first and most important for the peace of mind of the resident is that this beetle, and all beetles for that matter, is not a blood feeder. Beetles may bite humans in self defense, but I cannot think of any at this moment that actually bite or in any other way feed on living people. Dead animals, sure, but not live ones. Spider beetles in general are scavengers that feed on a wide variety of junk that they might find indoors. This includes grain-based food materials, but often foods that are not in very good condition, meaning they have sat around too long and may be moldy or otherwise in poor shape. It's possible that this kind of food resource might be stored in walls or attics by birds or rodents, so that cannot be ruled out. It also might just be some forgotten bag of food in the garage, laundry room, or even kitchen cupboards.
Spider beetles also feed on dead insects, spices, and even woolen materials that may be damp or moldy or have spills on them. Some spider beetles feed on fungi, such as molds or mushrooms. This makes it tough to narrow down exactly where these beetles in this apartment are coming from, but somehow somewhere there is a source that should be found and eliminated if the beetles are going to be eliminated as well. The good news is that spider beetles generally are only a nuisance, other than when they are infesting some food packages in the kitchen area. They can walk and most kinds can fly, so they could simply have found their way into the bathroom, perhaps to go to a lighted window, or if you are finding them only in that room it suggests a problem near to that area.
This is the value of magnification for ensuring a proper ID of any bug found in an account. Yes, the American spider beetle has a shiny black abdomen, and on first glance might be mistaken for a flea. But, under magnification it clearly is a beetle with long antennae and six long legs. This species also has yellow scales all over its thorax. But, pest control technicians often think inside the box, and may jump to an ID conclusion based on a narrow range of pests, such as fleas. If you had gone ahead and done a flea control job there it would not have resolved the problem and you would have applied insecticide unnecessarily. Good job for following up to ensure the ID.
This also strongly points out why we need to be the ones to verify what pest is present. Homeowners and other customers really have no idea what the vast majority of bugs look like. But, with something as trendy as bed bugs in the news there is a paranoia that anything that crawls is probably a bed bug, and again, if you had taken this person's word for it and gone ahead and done a bed bug control job you would have wasted a lot of your time and taken a lot of their money improperly. We always should find and ID specimens ourselves to verify the problem, and if this is not the law then it ought to be. You would be surprised at the growing collection of images I have of SEEDS that homeowners believed were bugs and were biting them.