Locust (24 page)

Uvarov was in increasingly dire straits. He went long periods without pay and often resorted to selling homemade pies in the market square before heading to the museum or university. He was despised by the Georgians as a Russian invader, he was being scrutinized by the Soviets as a member of the elite of the Russian Empire—and he was
the husband of an anxious wife and the father of a young son. Uvarov’s salvation came through his befriending Patrick A. Buxton, a British officer who was just two years his junior. They must have made an interesting pair—the slight, almost frail, entomologist and the strapping English officer. To Uvarov’s great fortune, Buxton was not only an intriguing companion but also well-connected to movers and shakers within the British government. Just a year later, Uvarov received an appointment to the Imperial Bureau of Entomology in London. He would not return to Russia for nearly fifty years.

Freed from the economic and social constraints of Soviet tyranny, the Uvarovs flourished in London. Boris and Anna allowed only the speaking of Russian at home, but they embraced their new life and were warmly accepted into British social circles. At the bureau, however, Uvarov walked a thin line. He was adept at using his supposed awkwardness with English to his advantage, choosing phrases that were painfully direct to the cultured sensibilities of the British. His convenient failure to find the suitably obtuse terms that sustained a genteel air meant that he could be stunningly direct and remarkably effective while skirting the edge of decorum. After a particularly grueling session with an advisory committee, Sir Geoffrey Evans sighed deeply and said, “Uvarov will never learn to understand our English ways!” In fact, Uvarov had become quite familiar with British obfuscation, but he’d found a clever means of avoiding the tedium and formality. Perhaps his approach would not have been as tolerated, or become as oddly endearing, if Uvarov had not also quickly become known as a scientist of tremendous intelligence and vitality. In addition, his small stature and dry sense of humor made his overwhelmingly powerful mind rather less threatening to those around him.

Uvarov’s new sense of opportunity and release infused him with the courage to put his ideas regarding the nature of locusts into print. His willingness to present his revolutionary theory to the world after a decade of incubation may also have been prompted by communications with a South African colleague, Jacobus C. Faure. Just as Charles Darwin’s publication of his theory of evolution was catalyzed by his realization that Alfred Wallace was close to arriving at—and publishing—the same ideas, Uvarov knew that Faure’s work with locusts in Africa was leading him to the same radical notion that
Uvarov had first glimpsed in the Northern Caucuses. And so, in the
Bulletin of Entomological Research,
now one of the oldest and most distinguished journals in entomology, Uvarov published “A Revision of the Genus
Locusta
with a New Theory as to the Periodicity and Migrations of Locusts.”

In his twenty-nine-page paper, Uvarov undertook what is called a
taxonomic revision
. In biology, the naming of species and their proper assignment to a particular genus are matters of continual investigation. Often we discover specimens or anatomical features that make us rethink whether a species has been properly described, named, and grouped. The goal is to have our taxonomy reflect the underlying biology that defines a species—the sharing of genetic material. Because we rarely have the time or opportunity (the seeming impropriety of biological voyeurism being of less concern) to follow creatures around and see if they are mating and then track the females to see if their offspring are viable, taxonomists use the bodies of organisms as surrogates for genetic similarity. Creatures that look the same presumably have a common gene pool. This approach has recently been challenged by our ability to more directly assess genetic similarity with molecular techniques. Zoologists are finding that sometimes animals that are physically indistinguishable do not share a genetic heritage. However, in 1921 Uvarov was struggling with the opposite problem. He was convinced that what earlier taxonomists had described as two species were really one.

Uvarov introduced his study by noting, “The literature on the economics, biology and especially on the means of control of these locusts is enormously extensive, but at the same time their systematic arrangement is in considerable confusion, and extremely contradictory opinions as to the mutual relationship of the different so-called species exist among specialists.” His particular concern was related to two species that to most people were so clearly different that no confusion should have been possible:
Locusta danica
and
Locusta migratoria
. The former species was a grasshopper leading a rather solitary existence and creating no fuss on the part of farmers. But the latter
species congregated in staggering numbers, maturing into the devastating swarms of migratory locusts that had caused famines for centuries in Central Asia. The ecologies of the two species were completely divergent.
Danica
was found in many habitat types, including dry grasslands, but
migratoria
was largely restricted to the basins of the Caspian and Aral Seas and Lake Balkash. The locust bred in the reeds of the river deltas, from where the immense swarms would emanate and sweep across the fertile irrigated farmlands of the region.

Based on anatomical appearances, the two species seemed to have very little in common.
Danica
was a bright green creature, whereas
migratoria
was quite variable but often black and orange red. The females of
danica
were much larger than the males, while in
migratoria
the sexes were nearly the same size. Uvarov also noted that the body of
migratoria
was very well suited for flight, with impressively elongated wings and a body filled with air sacs, which he noted were “described long ago by American entomologists in the Rocky Mountain locust, and occurring doubtless in all other migrating species of locusts.”

So, if the two species lived in different habitats, behaved in dissimilar ways, and looked markedly distinct, what was the problem? The problem was that Uvarov had witnessed the transformation of
danica
, the insectan Dr. Jekyll, into
migratoria
, the hexapodian Mr. Hyde.

 

In 1912, Uvarov had arrived in Stavropol, a town on the bridge of land between the Caspian and Black Seas, in time to see swarms of
migratoria
descending on the countryside. Such events were not at all unusual, but it was uncommon for a scientist to thoroughly sample the infestation and follow these locusts through the course of their subsequent generation. When the locusts hatched the next year, Uvarov found a mixed population of
migratoria
and
danica
, a most remarkable discovery given that there were absolutely no
danica
present in 1912. It seemed that
migratoria
was transforming into
danica
. To make matters even more intriguing, he soon learned that the reverse process was also possible.

In correspondence with his friend Vassily Plotnikov, who was working in Uzbekistan, Uvarov learned of experiments in which his colleague had reared
danica
in crowded cages. According to these
studies conducted in the summer of 1913, Plotnikov told his friend that “a number of them [nymphs] had the typical colouring of
migratoria.
” Uvarov, already a respected taxonomist, was sent some of these insects, and he confirmed that the parents were indeed
danica
and the offspring were well-defined
migratoria
. Plotnikov thought that perhaps they were seeing evolution unfolding before their eyes, and he suggested, “It is possible to suppose that this species is now in the process of splitting off from the primitive species.” But Uvarov had an even more intriguing explanation, one that would forever change our views of locust biology, ecology, and control.

Uvarov’s revolutionary paper included a three-page section, “The Theory of Phases,” in which he laid out his concept for
Locusta danica
,
migratoria
, and
migratoriodes
. This third creature was an African species that was indistinguishable from the Asian
migratoria
, but the two species had been named in the early days of entomology, when communications among taxonomists were erratic at best. Uvarov knew that a single widely distributed species was sometimes independently assigned different names by scientists working in different lands or languages. That took care of merging
migratoria
and
migratoriodes,
but what of
danica
? He made the radical argument that, “as a starting point, I take it as positively proved that the three forms cannot be separated specifically and that they represent taxonomic units of lower grade than the species, which must be called, according to the law of priority,
L. migratoria
.”

The law to which he was referring is the International Code for Zoological Nomenclature, which is a set of rules and standards originally developed by a commission of scientists in 1895. This code is one of the few international laws that seems to be both widely recognized and consistently enforced, perhaps because its provisions don’t really matter to the big issues of the modern world and the worst penalty for breaking the law is that everyone ignores you. Under this code, when a species has been mistakenly assigned two (or three or more) different names, the earliest given name is retained. Carolus Linnaeus, the Swedish-born Father of Taxonomy, had first named this creature
migratoria
in 1758. Thus, Uvarov used this name to unite the three, formerly distinct, species.

Uvarov then argued that the forms were not simply individual aberrations (such as genetic mutations), subspecies (a term used for different geographical races of a species), or seasonal forms (like the summer and winter coats of snowshoe hares or arctic foxes). He settled on a new term,
phases,
and stated that these phases—the solitary
danica
and the gregarious
migratoria/migratoriodes
—are manifestations of a single species that can be transformed from one to the other and back again. Although he wasn’t entirely sure of the factors causing the phase transformations, he knew that they were somehow associated with external conditions and strongly suspected that population density played a role. In this sense, the phase theory was much like Darwin’s evolutionary theory: In both cases the process of biological transformation was correctly identified, but the underlying mechanisms were not understood. The mechanisms of genetics and the structure of DNA eventually revealed the workings of evolutionary change. And we have now pieced together the ecological triggers and physiological mechanisms of phase transformations.

Different organisms have adapted in various ways to the boom-and-bust cycles of productivity that typify continental climates, and the locusts evolved phase change as a means of tracking ephemeral resources. During normal years, the locusts persist in their solitary phase, generally avoiding one another to more evenly exploit the available resources. In moist years, their populations begin to increase within their breeding areas. This increase may be sufficient to cause crowding in some habitats such as deserts, where food is normally scarce. In habitats with more reliable food, such as grasslands and meadows, crowding occurs when productive periods are followed by droughts that force the abundant insects into close contact while competing for declining food. In either case, the gregarious phase is triggered by the insects’ endocrine system, which is cued both by chemicals released from the crowded insects via their accumulating excrement and by the frequent disturbance of tiny hairs on the hind legs of the creatures.

Although outwardly unchanged themselves, the crowded females lay eggs that are biochemically predisposed to develop into nymphs with a predilection for aggregating rather than scattering. This tendency is reinforced as the growing nymphs are compelled to congregate
in the shrinking patches of lush grasses, caused by overpopulation, the onset of drought, or both. The constant jostling and odor of feces continue to induce endocrine changes that complete the locusts’ transformation into the migratory phase. The changes in the insect’s morphology (such as lengthened wings), behavior (such as the propensity to aggregate), and physiology (such as the delayed maturation of eggs) are all in preparation for migration. For locusts, crowding means an impending famine, and migration into the unknown is preferable to sure starvation.

Of course, this process of transformation is entirely reversible. As the population density declines due to a swarm’s being dispersed or suffering high mortality, the cues that elicit development of the gregarious phase diminish. The eggs laid by scattered adults tend to develop into rather unsociable nymphs. With low densities and solitary behavior, the nymphs rarely encounter one another (or other locusts’ feces). And so, the locusts transform back into their solitary phase until such time as environmental conditions induce a surge of reproduction, a period of crowding, the possibility of famine, and the compulsion to migrate.

If the phase transformation process of locusts were applied to humans, we would find that an economic downturn had caused our neighborhoods to smell like a sewer and our fellow commuters were constantly pushing and shoving us on the way to work. These sensory insults would trigger hormonal changes turning us into a mob of anxious, red-faced neurotics with a reduced libido and an intense desire to charter a fleet of planes. As the planes unloaded us along the way (or perhaps our ranks thinned by plane crashes), our population density would decline. The stench and jostling would diminish, and we would revert to reclusive, pale-faced homebodies. Perhaps locusts and humans have more in common than we suppose.

Although Uvarov did not understand the biochemical mechanisms, he correctly predicted that the capacity of locusts to radically change their form and function was not restricted to the species that he had investigated. He made explicit mention of Faure’s work on the Brown locust of South Africa, noting, “These valuable observations of Mr. Faure’s leave no doubt that
L. pardalina
has, like
L. migratoria,
two
different phases, which differ in morphology and coloration, but more profoundly in the biology.” So whereas Darwin was reluctant to share the limelight of evolutionary theory with Wallace, Uvarov took pains to credit his colleague: “The above-quoted conclusions of Mr. Jacobus C. Faure concerning the transformation of the solitary phase into the swarming one, at which he arrived quite independently of my work on
migratoria,
give a very strong support to the theory of phases as a direct cause of the periodicity.”