Sleep Tight . . . Evolution's At Work

Opening Comic Relief

Cul De Sac, the comic strip by Richard Thompson, features four-year old Alice Otterloop who tries to make sense of life.  In the strip that ran on January 9, 2011, her older brother Petey does what all older brothers do, they let younger siblings in on the secrets of the world.  In this case, it’s about the little, dirty trolls that live on the huge soot covered mountains of snow that, in the northeast, dominate shopping mall parking lots during the winter.  (The Otterloops live in the D.C. area; their last name is Thompson’s play on the “outer loop” of the Beltway, the highway that encircles the city.)

According to Petey, these trolls, or Sooti, capture and take “unwary bargain-hunting shoppers to their doom.”

Alice:  Really?

Petey:  That’s why you find abandoned shopping carts everywhere.

Alice:  Wow.  Nature is so cool.

(Alice’s exclamation got me, but, it’s not the final punch line.  Alice’s mom comes upon a cart and says, “Look!  Here’s a cart, and somebody’s left all their coupons in it!”)

Let the Horror Begin

Nature is so cool.  Sure is, though nature’s reality can be even stranger, and more unsettling and monstrous than Petey’s mythical Sooti.

This post explores a strange, unsettling monstrosity that nature has actually produced.  It’s a tale of evolution, striking with a vengeance.

Late last year, when I made plans to travel out of state and spend several nights in a hotel, I did all of the usual scouting on the web for room availability and good prices, but I also did what the seasoned and rational traveler now and for the foreseeable future will do, I consulted such web sites as the Bed Bug Registry to see if that wonderfully priced hotel room came with a dark secret (or a secret hiding in the dark).

Though in the U.S., awareness of bed bugs largely faded away in recent decades, there’s now the sickening realization that they’ve reentered our lives.  Just like Sheridan Whiteside in the 1930s Kaufman and Hart play The Man Who Came to Dinner, these creatures have come to stay, sleep in your bed, and quite possibly take over the house.  Whiteside’s terrorizing of his hosts was comic and benign, these creatures employ subtle and devastatingly effective methods of prolonged torture.  Think tiny vampires, only really, really scary ones.

The common bed bug is Cimex lectularius, the species of this family that has “most adapted to living with humans.”  (Michael F. Potter, Bed Bugs, University of Kentucky’s College of Agriculture.)  It is a member of the Family Cimicidae and, as a member of the Order Hemiptera, it is identified scientifically as a true bug.  Its scientific name is spot on.  According to the wonderful Dictionary of Word Roots and Combining Forms by Daniel J. Borror (1960),  the Latin roots for its scientific name are Cimex for “bug” and lectul for “couch” or “bed.”

For this post, I decided keep the threat level down and not include a photograph of one of the little beasts (they are under 1/4th inch in length as adults).  Instead, here’s a drawing of a female of the species; it appeared in the 1896 U.S. Department of Agriculture’s publication The Principal Household Insects of the United States (p. 32)  (Still rather creepy.)

I traveled a couple of weeks ago with two critical items in my suitcase – a copy of the Washington Post’s Urban Jungle column for December 14, 2010 (titled Abominable Holiday Hitchhikers - at this website, go to the #2 entry for December - you might also get a popup, the bed bugs of the web), and, from Cornell University’s New York State Integrated Pest Management Program, the handy wallet sized guide, Bed Bugs:  What Travelers Need to Know .  Both items are very useful and dispassionate about all of this, with steps to take when you travel.  There are other good resources on the web, including those prepared by the Centers for Disease Control and Prevention.  One of the best introductions to the scientific literature on C. lectularius is Biology of the Bed Bugs (Cimicidae) by Klaus Reinhardt and Michael T. Siva-Jothy, which appeared in the Annual Review of Entomology (2007).

As I explored C. lectularius, I kept returning to a question, “Why have bed bugs returned to prominence now?”  Several reasonable hypotheses have come from the scientific community; for irrationality, turn to the blogosphere which, in some areas, is awash with misguided political and economic thought about this issue.

Let’s start with the off base and oft repeated assertion that the widespread use of DDT had forced the damned bed bugs to their little arthropod knees and that the pesticide would have delivered the knockout punch then (or now) if only it hadn’t been banned in the U.S. in 1972.  Here’s just one example that ran in the Santa Clarita Valley (California) Signal on August 30, 2010:

Bedbugs, a common household pest for centuries, all but vanished in the 1940s and 1950s with the widespread use of DDT.  But DDT was banned in 1972 as too toxic to wildlife, especially birds.  Since then, the bugs have developed resistance to chemicals that replaced DDT.

Groups on the right use this kind of inaccurate conclusion in their general condemnation of government environmental regulation, blaming the ineffectiveness of current pesticides and the bed bug resurgence on the federal government and its intrusion into workings of the free-market (see Bedbugs Taking A Bite Out of New Yorkers from the libertarian Heartland Institute).

Such an argument conveniently ignores the decline in the use of DDT prior to the ban in 1972.  DDT was already no longer as effective as it had been because evolution was at work; insects, including bed bugs, had been developing resistance to the pesticide.  The director of government affairs for the National Pest Management Association has been quoted as saying, “Bloggers talk about bringing back DDT [to address the bed bug explosion], but we had stopped using it even before 1972.”  (Jerry Adler, The Politics of Bedbugs, Newsweek, September 8, 2010)

In fact, evolution is already implicated in the limited effectiveness of current pesticides, but in an interesting way.  According to the University of California’s Museum of Paleontology on its Understanding Evolution website, by virtue of natural selection, a few key genetic mutations that limited the effects of DDT spread had appeared in the bed bug population during the DDT tsunami.  Those mutations spread among the surviving bugs.  Apparently, even then, thanks to evolution, the bed bug was on the way back.

Although, with the DDT ban, those mutations were of less utility to the insect, they were nevertheless carried on from generation to generation.  Apparently, the pesticides that are the current “top choice” for dealing with bed bugs are pyrethrums; unfortunately, they work much the same way as DDT did – attacking the insects’ nerve cells.  So, the current batch of bed bugs comes prepared for our most popular chemical weapons.  Hardly the fault of government regulation, and, perhaps, in truth, the result of unregulated application of DDT in the 1940s through 1960s.

Further, the diminished bed bug population in the latter half of the 20th century cannot be attributed solely to the impact of DDT; other changes probably contributed as well.  Among those mentioned in the literature are improvements in personal hygiene, the impact of vacuum cleaners as they worked their suction magic, and regulation of the used furniture market.

So, what’s changed to cause the current plague?  Here are the some of the hypotheses put forward by scientists studying the issue.  In addition to the fact that C. lectularius has resistance to current pesticides, it has been suggested that the resurgence may be blamed, in part, on some combination of changes in tactics by the pest management industry (a broader use of baiting to control insect infestation, an approach that, unlike spraying, has little ancillary impact on bed bugs); a certain lack of attention to the issue by the hospitality industry; and increased international travel and commerce, particularly involving locations where bed bugs never took a real hit.  (See, for example, information posted by the University of Kentucky’s College of Agriculture and the Ohio State University Extension.)

Where did bed bugs come from in the first place?  According to the David Grimaldi and Michael Engel, entomologists and paleontologists with the American Museum of Natural History, although the superfamily Cimicoidea probably arose in the Late Jurassic, the Cimicidae are a product of the Eocene, concurrent with the appearance of bats on which the early version of Cimicidae members supped.  (Evolution of the Insects by David A. Grimaldi and Michael S. Engel, 2005, p. 329-330)  I came across speculation that C. lectularius may have evolved from that blood sucking bug that lived on bats.  When hominins started living in caves, perhaps some of these insects took advantage of the opportunity to enjoy a larger snacking area. (J.B.S. Haldane, The Causes of Evolution, originally published 1932, p. 5).

Cimicidae are of particular interest to evolutionary biologists for another reason, one that makes these vile creatures even worse.  The sex habits of the males of the entire bed bug family really pushes them to the top of the villain scale.  I wont go into any detail except to say that the male’s act is called “traumatic insemination” and the average life span of females is some 30 percent shorter than that of males, even though, in this sexual arms race, females have evolved to reduce the effect of this method of insemination.  More, if you want it, appears in the article I cited earlier, Biology of the Bed Bugs (Cimicidae) by Reinhardt and Siva-Jothy, or, to get right to the point, take a look at Costly Traumatic Insemination and a Female Counter-Adaption in Bed Bugs by Edward H. Murrow and Gören Arnqvist, Proceedings of the Royal Society B, September 10, 2003.

Closing Comic Relief

Lest you think that bed bugs are just another media-hyped frenzy, I know I am perfectly justified to be as obviously obsessed as I am because bed bugs have registered on the Dave Barry barometer of the real and profound.  Dave Barry's Year in Review: Why 2010 Made Us Sick has this entry for October, 2010:

On the legal front, the Supreme Court, as it does every October, begins a new term, which is hastily adjourned when the justices discover that their robes have bedbugs.

Okay, maybe the bugs aren’t really in the robes . . . yet.