[The Envelope Please...] Urban Entomology's Greatest Hits

What exactly is “urban entomology”? Since its emergence as a catch phrase in the 1970s, it usually refers to the study of pest species in structures to ultimately improve their management. Indeed, Walter Ebeling’s pioneering textbook on the subject (which served to popularize the concept and give it an academic identity) was dedicated to “the pest control operator, in recognition of his contributions to health, comfort, and quality of life in the urban community.”

That’s an eloquent testament and well deserved — but I believe the emphasis, since Ebeling’s time, on practical applications has served to hinder a general understanding of the true scope and significance of this discipline. In my travels throughout both the pest management industry and academia, I get the distinct impression that too many people do not fully appreciate both urban entomology’s diverse achievements and its continuing potential to enrich other fields of human knowledge beyond its core constituency.

And so, in order to publicize the breadth and depth of this subject area, a new series of distinguished accolades has been established — just now — to honor world-class practitioners of the urban entomological arts whose results have transcended the expected. These prizes have been named the Ebeling Awards, in honor of urban entomology’s founder. I wish I could say the honorees were selected by a blue ribbon panel of judges, but that would be stretching it — I’ve never won a ribbon for anything. Evaluation criteria for the nominated scientific performances were: 1) a focus on one or more species prominent in the urban ecosystem, 2) an obvious applicability to broad scientific or cultural themes, and 3) that certain je ne sais quoi of attention-grabbing dazzle. It was considered to be way cool if the work actually contributed to more effective pest management approaches, but this was not required. As it turns out, four out of the five initial prize winners indeed have had a dramatic impact on our field. In the aggregate, they mirror the eclectic array of topics and approaches that constitute the increasingly dynamic discipline of urban entomology.

The award itself is affectionately known as an “Ebby,” i.e. a gilded statuette of a cockroach proudly holding aloft a globe-type thing and bearing an uncanny resemblance to another well-known award in the performance arts. Alas, due to a severe funding shortfall, the statuette is virtual only.
So without further ado, grab some popcorn and let’s get to the citations!
 
THE EBELING AWARD FOR ETHOLOGY — Subsocial Behavior in Cat Fleas. Honoree: Anneliese Strenger (1913 – 1984). When I was first beginning my career, the 3rd (1960) edition of the Mallis Handbook, hot off the press, concisely stated this prevailing belief about flea biology: “The small whitish larvae feed on any organic material found in the nest of the host or in the house where the eggs are laid.” Nowadays it is taken for granted that larval cat fleas (our most important pest species) in nature cannot survive without a diet of adult flea feces, consisting mostly of dried, undigested blood, which fall off the host and conveniently accumulate in the same places as the eggs. These sites — mainly the host’s resting spots — essentially function as communal flea nurseries, since the offspring from numerous females are being indirectly fed by multiple adults of both sexes in addition to their own parents. Nonviable (trophic) eggs laid by the female fleas are also a critical larval food.

The biological significance of this arrangement is huge. Any old bug can be a random scavenger, but it takes a special sort of bug to evolve subsociality. Strictly speaking, this term denotes parental care, the first evolutionary expression of social behavior. And what a distinctive type of care it is! The only other well-known obligate coprophagy (mandatory fecal eating) in insects is anal trophallaxis in termites, which ensures the young get inoculated with essential, cellulose-digesting gut microbes.

Strenger was already a renowned morphologist at the University of Vienna when she published the article in 1973 that first set out this fundamental revision of flea biology. Its impact on our own research community was slow to develop (undoubtedly because it was written in German). Then in a golden period of intense flea research during the 1980s and early 1990s, several groups of urban entomologists elaborated upon the parental feeding concept, filling in additional critical details and widely promoting its practical implications to the pest management industry. The result was a far more effective and efficient flea treatment strategy defined by the resting behavior of pets, rather than indiscriminately hosing down the entire property. Flea control has since shifted much of its focus to the veterinary community, but this significant contribution to insect ethology will echo through the ages.
 
THE EBELING AWARD FOR EVOLUTION — Genetically Distinct Mosquitoes in the London Subway. Honorees: Katharine Byrne, Richard Nichols. During World War II, Londoners seeking shelter from the Blitz in their city’s subway tunnels found themselves attacked by voraciously biting mosquitoes. The aggressive pests, long familiar to maintenance workers in the underground system, looked identical to the surface-dwelling Culex pipiens, the world’s most widely distributed mosquito and one which was thought to feed mainly on birds. Amazingly enough, the troglodytic (i.e. subterranean) forms were largely ignored by scientists until fairly recently.

Their story was finally pieced together by the intrepid Byrne, who logged many soggy midnight hours in the tunnels. The subway mosquitoes spend their entire lives underground and feed almost entirely on mammals. They are able to mate in confined spaces, can lay eggs without a blood meal, and have no winter diapause. In contrast, the ornithophilic (bird-biting) C. pipiens living above them must mate in unrestricted flight, require a blood meal to oviposit, and become dormant during the cold season. The subterranean and surface populations are genetically distinct, with no evidence of gene flow between them.

It sure looked like one of the “holy grails” of urban biology had been found, that of natural speciation due to intense selection pressures in a man-made ecosystem. The study’s 1999 publication caused a sensation in the popular scientific press, and it wasn’t long before the subterranean mosquitoes became a football in the evolution vs. creationism debate as an example of rapid and observable evolution occurring — so to speak — under our noses.

As it turns out, more recent work has showed that the tunnel populations in all likelihood started out as a chance introduction of a genetically-distinct form (C. molestus) from southern Europe that is behaviorally predisposed to colonize such habitats. In fact, the prevalence of hybrids of the two strains in North America may well be the reason that our Culex mosquitoes are so much more likely to transmit West Nile virus from birds to humans than in northern Europe. Nevertheless, we are indebted to Byrne and Nichols for painstakingly describing a fascinating and neglected corner of the urban environment that might otherwise remain unexplored.
 
THE EBELING AWARD FOR PHYSIOLOGY — Resistance to Glucose Ingestion by the German Cockroach. Honorees: Jules Silverman, Donald Bieman. Evolution is also a theme in this well-known chapter of modern pest management lore. There are still many of us who remember 1) the unbridled optimism when hydramethylnon bait stations became the new IPM standard-bearer in the 1980s, decimating German cockroaches in both residential and commercial accounts, and 2) the profound dismay (mingled with a sense of impending doom) when reports began trickling in after only a few years that the product had begun to dramatically fail in some locations. Resistance rearing its inevitable head again!

But what a twist on the usual suspect. In a 1993 report that became an instant classic, Silverman and Bieman conclusively demonstrated that the culprit was not tolerance to the active ingredient but aversion to a basic component of the bait — a substance known as D-glucose. The term “behavioral resistance” was quickly added to our lexicon.

Its physiological implications were astonishing. Glucose is a simple sugar that is the most important carbohydrate in the world, essentially a universal metabolic fuel in both plants and animals. From bacteria to humans, it is the principal end product of the digestion of most foods, and thus serves as a powerful feeding stimulant for many animals when already available in their environment. Rapidly evolving an aversion to a molecule as ubiquitous and fundamental to life’s functioning as glucose is roughly akin to suddenly being repelled by water — and being able to live anyway. As part of an ever-expanding demonstration of how insects have been able to reinvent themselves on short notice to shifting selection pressures, this stands out as one of the most remarkable.
 
THE EBELING AWARD FOR MEDICINE — Cockroaches as a Critical Source of Inner City Asthma. Honoree: Bann Kang. Much of the structural pest management profession consists of patiently dealing with pests that are relatively innocuous in the grand scheme of things but that traumatize an anxiety-ridden general public nonetheless. This award pertains to the opposite end of the spectrum.

Working as a young, impressionable exterminator in Manhattan low income housing in the 1960s, I saw for the first time what a German cockroach infestation looks like when all available crevices become fully infested. The masses of them clustered on the window curtains evoked images of the insides of tropical caves. Their sweet, acrid stink was overwhelming. My eyes swelled, breathing became difficult, and I was grateful I did not have to come home to this type of life.

Of all the suffering caused by structural pests, the illness and even death that characterizes cockroach-caused allergic asthma — particularly in children — is certainly the most widespread and severe. All the more surprising then (in retrospect) that it took scientists so long to figure out the connection. And although the prevalence of hypersensitivity to cockroach allergen had been widely recognized by the 1970s, one person is most closely associated with work during that decade and into the 1980s that finally nailed down the relationship of prolonged exposure to cockroaches with debilitating asthmatic reactions among the urban poor — our award winner. In the years since she led the way, the impact of cockroach allergy on human health has been increasingly appreciated and a growing number of other common indoor pests have been implicated in a similar role.
 
THE EBELING AWARD FOR PSYCHOLOGY — Mitigation of Physician-Mediated Mass Hysteria Over Fictitious Spider Bites. Honoree: Rick Vetter. One of the deepest and most widespread phobias in Western society is the fear and loathing of spiders. Bad enough when this (mostly) irrational affliction causes unwarranted anxiety in daily life, but it’s flat out inexcusable when it becomes a controlling component of medical diagnoses involving mysterious sores on the skin.

Ever since bites of the brown recluse spider (Loxosceles reclusa) were identified in the 1950s as sometimes causing large, slow-healing necrotic lesions, physicians all over the country have been on a roll in automatically blaming the arachnids for any similar-appearing injury. Never mind that diagnoses are made in the absence of any collected spider; that most bites of this species are minor; that they are extremely reluctant to bite and do their best to avoid human contact; that they don’t even occur in many parts of the country where “recluse bites” are diagnosed; and, most importantly, that there are dozens of other conditions (such as bacterial infections) that will produce nearly identical sores. Infatuated with the mystique of loxoscelism, too many doctors have enthusiastically wallowed in the depths of their own ignorance and misled countless patients into believing they’ve been victimized by a spider.

However, for the past 10 years, one arachnologist has relentlessly fought this epidemic with a barrage of publications painstakingly supplying the antidote of factual information about recluse spiders and the hysteria surrounding them. Vetter’s tireless crusade has been waged with equal measures of scholarship and showmanship. His fundamental strategic insight has been to take the battle to the physicians’ turf, collaborating with medical professionals and publishing in medical journals. Due to his efforts, the tide has now actually begun to turn, with a growing awareness of loxoscelism misdiagnosis syndrome emerging throughout the medical community. It’s not the broader biological literacy we’d like to see in our doctors, but it’s a heck of a start.

The author gratefully acknowledges Dr. Nancy Breisch for patiently tolerating ventures considerably odder than concocting his own series of scientific awards. The opinions expressed herein are the views of the author and do not necessarily reflect the official policy or position of the U.S. General Services Administration.

Al Greene is regional entomologist and national IPM coordinator for the U.S. General Services Administration, Washington, D.C.