The following is not my story, but it’s still a good one, with a lesson to teach about how the human mind interprets the natural world. The principals in the story have been kind enough to let me retell it, though they prefer, quite reasonably, to remain anonymous. Though they come across quite credibly in the story, I am happy to call them the Smiths. The tale begins a little over a year ago, when the Smiths hosted itinerant friends in their seasonal home. Tidying the room after the friends left, the Smiths were appalled to find a tiny, flat bug on a pillow, with the unmistakable overall look of a bedbug.
There are, of course, few better ways to freak out a homeowner than the discovery of bedbugs. Whether these blood-drinking human commensals actually carry disease appears to be an open question. But strong anticoagulant produced by bedbugs means that they leave behind weeping, bloody bite sites. And these insects are notoriously hard to eradicate once they become established in a dwelling.
The Smiths, then, had the unenviable tasks of letting their houseguests know what they had left behind, and then declaring war against the insects. A series of escalating measures — laundry, deep cleaning, installing physical barriers to keep bugs from climbing onto the bed — produced no more than temporary relief; after a little while, more bugs would show up.
Leaving the house closed up and the room sealed for the winter didn’t work, either. The house was initially bug-free in the spring (one of the Smiths, boldly, slept in the affected bedroom as a test). But before long, another live bug turned up on the floor.
Ultimately, the Smiths invoked the nuclear option: They purchased a device that turns a room into a large, low-temperature oven, cooking any bedbugs along with, presumably, everything else. But no joy! Despite repeated cookings, bugs kept turning up.
Around this time, the Smiths noticed something that dramatically changed the picture: bugs, not on the floor or the bed, but on the ceiling. By all accounts, that’s unheard-of for bedbugs. Moreover, the Smiths had never observed the eggs, larvae, or molted exoskeletons that one might expect to find as evidence of the full bedbug life cycle. There was also the perplexing fact that, despite the intermittent presence of the bugs across a full year, nobody had been bitten.
I should mention that the Smiths are both pretty fair naturalists, accustomed to thinking in terms of ecological relationships, life histories, and animal behavior. Things were not adding up; the Smiths recognized that fact; and that led them to the critical question: Might they have diagnosed bedbugs without being aware of other options?
Closer examination suggested that bugs were using a tiny hole by a ceiling fan to enter the room from above the ceiling. A little web searching revealed the existence of bat bugs — news to me as well as to the Smiths. In fact, there’s an entire taxonomic family (a small one, but still) comprising bloodsucking ectoparasites that all share the compressed gestalt of the bedbug. Roughly 15 species of the family Cimicidae in North America, and considerably more than 100 species worldwide, are optimized for use of specific animal hosts. Only two species in this morass of parasitic insects routinely bite humans.
From that point, the Smiths rapidly solved their puzzle. Examination outside the house revealed bat droppings on an air conditioning unit adjacent to the affected bedroom. The Smiths, in short, had bats in their belfry; the bats carried bat bugs; and periodically, a few bat bugs would drop down into the room below, impersonating their bed-loving, human-biting relatives.
Using internet resources, the Smiths determined that their intruders were indeed bat bugs. Later, under a microscope, I was able to confirm the I.D., with the Eastern bat bug, Cimex adjunctus, my best guess for the species (there are several bat-biting Cimex species). Mystery solved!
There was still work to be done. Bat bugs, while preferring bats, have been known to bite humans as a desperation measure. So a permanent solution was still very much in order. Moreover, one really doesn’t want mammals of any kind living in one’s attic. But caulking around the ceiling fan successfully excluded bat bags from the house. And a plan is in place to kill any remaining bugs, and bat-proof the structure once any breeding bats have raised their young and moved on.
Upon finding what looks like a bedbug on a bed, it’s reasonable to conclude that you’ve got bedbugs. The mind sees what it expects to see. Bedbugs loom large in our consciousness, so why would anyone even imagine that other possibilities exist? It certainly didn’t occur to the Smiths — until the moment when it did. Now they know, and so do we. That’s how we naturalists roll.