The screw worm takes the grisly story of being eaten alive a little further. The “screw” that gives the worm its name is actually a series of concentric spines. The maggots operate as a cluster: they secrete an extra digestive enzyme within the wound to smooth their progress into the flesh by turning it into soup. The barbs of the spines interlock so that the maggots cannot be dislodged by the rasping licks of an ox tongue. As the maggots move inwards they continue to breathe through their stubby back ends by means of spiracles—the openings to these “lungs” can be seen as tiny dark dots. The definitive screw worm is a New World fly, Cochliomyia hominivorax (the species name is the Latin equivalent of the Greek anthropophaga of the tumbu fly), which is particularly prevalent in Mexico and central America. It can progress from larva to pupa in under a week, and since an adult fly can travel many kilometres and lay thousands of eggs, these flies can quickly become a plague. They can reduce a cow to pulp. Even where the fly is native it is a scourge, but if it escaped into a place where animals were unprepared for it, the consequences could be disastrous. As its scientific name implies, the screw worm can feed on humans, too, in a comparable fashion. This is how it was first discovered. The French entomologist Charles Coquerel described the species in 1858 from a specimen taken from a man who died at Cayenne, the infamous penal colony in former French Guyana. It is in all our interests to stop the spread of this alarming creature, which is the point at which Martin Hall comes back into the tale.
The feeding head of the larval screw worm Cochliomyia
In 1989 Martin Hall went to Libya and found screw worm larvae in the herd belonging to the Ministry of Agriculture. He told me it did not take him more than a few seconds to recognize the characteristic dark spiracles of C. hominivorax. The parasite had probably been introduced from South America in imported sheep. The Libyans did not like his diagnosis at all, and Martin was forced to raise some of the maggots in his hotel room to prove his point. He is not the type of man to let his expertise be challenged. Imagine if the screw worm were allowed to escape into Africa unchecked. Not only would domestic cattle suffer appallingly, but the fly would have wrought havoc on all the wild bovids across the continent, all those wildebeest and hartebeest and their relatives. The infestation could well have pushed rare species into extinction. It would have been an unprecedented catastrophe for an already blighted continent. In the Libyan context it was particularly galling that a common name for the parasite is the “American screw worm”—paranoid explanations of the infestation were bound to follow. Something had to be done to eliminate the pest, urgently. The technique used was sterilization. The idea was to release vast numbers of sterile male flies into the wild among the herds. If enough were liberated in this way, the chances of a female coming across a fertile male would be small; mating would lead to duff eggs at best; repeat the process several times and the viable breeding population would shrink to nothing. The crisis would be averted. The technique used involves sterilizing the males at a late pupal stage, by exposing them to a radioactive isotope of the element Caesium Cs135. This is late enough in the development of the insect to produce a male normal in all other respects, including sex drive. The figures are extraordinary: sixty million pupae a week were air freighted from Mexico to Libya during the eradication programme. The logistics of producing so many maggots and pupae require that they are fed on massive quantities of a rather unpalatable meat pâté, a case of Wormy writ very large. Sterilization as a biological control was invented by Edward Knipling, whose name should feature with those of Edward Jenner and Louis Pasteur in the pantheon of those who rescued humans from misery. In 1995 was awarded the Japan Prize, which is almost the same as a Nobel, though less well known outside the scientific cognoscenti. As for the Libyan outbreak, the release of sterile males was continued until six months elapsed without capture of a fertile fly. With one bound, and billions of pupae later, the cattle were free. All this was achieved because an expert knew his maggots…The outcome is a plaque in the Food and Agriculture Organization of the United Nations, and the screw worm is now a “notifiable” pest at the Office of International Epizoology in Paris.
The price of freedom from flesh-eating flies is eternal vigilance. The kind of molecular evolution studies that we have already met in describing schistosomes confirm what many entomologists had suspected: that this nasty behaviour has arisen several times from different ancestral flies. The carnivorous flies in question appear on separate branches of the evolutionary tree, cousins under the skin. The Old World screw worm is called Chrysomyia bezziana (“Bezzi’s fly”—and who would like such an animal named after him?) and learned its grisly trade independently of its New World counterpart. It is a native of sub-Saharan Africa and Asia. This species particularly infects open wounds, burrowing in using special hooks, and if such lesions are left untreated the parasite can cause permanent disfigurement. It is not averse to burrowing into soft fleshy folds elsewhere on the anatomy, rather like the gusset fly. Chrysomyia has arrived in the Middle East: in Iraq between the first and second Gulf Wars; in Bahrain, probably on shipments of sheep brought in to feed a growing population. Imported Arab horses are another possibility. Of the four horsemen of the apocalypse, only pestilence could be carried on the steed itself.
There are, of course, lesser parasites. The louse is an inconvenience rather than a death sentence. “Lousy” as an adjective does not rate as the absolute nadir; it’s more of a generally disgruntled word, a crosspatch’s rejoinder to a formulaic question about the state of his health.*17 The human louse has been having a lousy time of it in western countries since the 1950s; once ubiquitous, the head louse hangs on persistently in schools, and still sends a shudder through a mother who finds its “nits” (egg cases) on her children’s hair. The louse was named scientifically, it will be unsurprising to learn, by Carolus Linnaeus himself: Pediculus humanus. There are two different subspecies, living on head and body (capitis and corporis) respectively; the pubic louse (“crabs”) Phthirus pubis is more distantly related. In nature there are some five hundred other species of lice living on many other hosts. One of the curators at the Natural History Museum responsible for lice was Bruce Frederic Cummings, who joined the staff in January 1912. He had—too grim for irony—a lousy time. He was dying from multiple sclerosis, what was then known as disseminated sclerosis. He was forced to resign from the Museum in 1917 because of ill health. But he recorded his struggle with decline in a remarkable memoir compiled from his diaries. His extraordinary account was published in March 1919 under the title The Journal of a Disappointed Man. Cummings wrote under the nom de plume of W. N. P. Barbellion. The initials W. N. P. stood for Wilhelm Nero Pilate, the author’s selection of the most despicable people in history; Wilhelm was of course Kaiser Bill, this being the time of the First World War. Barbellion was a name emblazoned above a shop in South Kensington that Cummings passed every day. The Journal is a work of introspection so intense and unflinching that it leaves the reader exhausted. There is fury at his loss of hope, but since Barbellion was incapable of turning a dull phrase the text is also somewhat exhilarating. Of his wasting disease he writes: “Why this deliberate, slow-moving malignity? Perhaps it is a punishment for the impudence of my desires. I wanted everything so I get nothing…I am not offering up my life willingly—it is being taken from me piece by piece, while I watch the pilfering with lamentable eyes” (5 July 1917).
The plaque recording the part that taxonomy played in the eradication of the New World screw worm from Africa
Several distinguished writers viewed his work with favour. H. G. Wells wrote the introduction to the Journal, and Marcel Proust and James Joyce were admirers. Other critics thought the work immoral and self-indulgent. The Journal is a hodge-podge of stories, health reports and observations on decline, which are riddled with guilt and illuminated by ecstatic flashes. It is impossible not to feel sympathy for this hypersensitive soul in perpetual torment. His time in the Natural History Museum was not in any sense a ha
ppy one. He was clearly devoted to zoology, and returns to this infatuation with the regularity of a mantra. He taught himself comparative anatomy from specimens borrowed from the Plymouth Marine Laboratory. He desperately wanted to be a professional natural historian. “In the repose of the spacious laboratory by the sea, or in the halls of some great Museum, life with its vulgar struggles, its hustle and obscenity, scarcely penetrates. Behind these doors life flows slowly, deeply” (4 March 1911). He wanted to know everything, to suck in the whole of nature, but was awestruck by the limitations of his memory and his persistence. He equally wanted to experience the life inside every pub and on every street corner—and women: he had an unquenchable voracity for experience, even as his health dictated a contraction into neurasthenia and introspection. He certainly did not wish to be any kind of functionary in the natural history world. “I don’t want to be worrying my head over remedies for potato disease, or cures for fleas in fowls. Heaven preserve me from becoming a County Council lecturer or a Government Entomologist” (30 June 1911). The latter is exactly what he became. He yearned to be a great comparative anatomist, the Richard Owen of his day. Instead, he was destined to write pamphlets on lice, even as his serving contemporaries suffered from their unwelcome attentions in the trenches—an ordeal he was too unwell to share. He felt he was intended for nobler things. “I gave evidence as an expert [his italics] in Economic Entomology at the County Court in a case concerning damage to furniture by mites for which I am paid £8–8s fee and expense and travelled first class. What irony!” (8 October 1913). There is something of disdain for the commercial creature in his attitude. He wanted to fly nobly above the commonplace, to be admirable and remarkable and justly famous. He excoriated himself for failing to achieve his dreams, and yet how realistically he knew that they were just dreams. He was in many respects a thoroughly modern antihero. He wanted to know all of zoology, yet found that reading even one number of the German scientific journal Zoologische Anzeger cover to cover was beyond him. “Zoology alone was sufficient to baulk my puny endeavours,” he wrote in 1913. “How hopeless it all seems!” He continued: “I shot up like a ball on a bagatelle board all steamy with zoology (my once beloved science) but at once rolled dead into the very low role of Economic Entomology! Curse…Why can’t I either have a first-rate disease or be a first-rate zoologist?” It is that phase in parentheses—“once beloved” zoology—that saddens me. Everything, even the zoology he preferred to money or fame in his early diary entries, was subsumed under his existential gloom. The Museum was no cure; instead it became just another symptom.
Bruce Frederic Cummings, a.k.a. W. N. P. Barbellion, author of The Journal of a Disappointed Man
A little further down the scale of parasites we have the flea. And the complete antithesis of poor Bruce Cummings was the world authority on fleas, Miriam Rothschild. Where Cummings was woefully insecure and met an untimely death, Miriam Rothschild had the confidence that comes with a famous name and a considerable fortune, and she lived to a great age. Her long life overlapped with that of Barbellion, and lasted into the age of biological molecular sequencing. The Rothschild family is one of those dynasties that almost everyone is aware of in a general way but whose details slip away untouched in a welter of discretion. There are three branches of which I am aware: the bankers, the wine makers and the natural historians. No doubt there are more twigs, and they certainly interlink in complex ways, since some of the naturalists were also able bankers. The bankers still own one of the last great private merchant banks in the City of London. This is a hermetic world that makes the back rooms of the Natural History Museum seem almost like public property. As the historian Niall Ferguson has explained, these Rothschilds interceded in the big events in history in an ever so understated way: Who else would or could have financed the purchase of the Suez Canal for Queen Victoria? The wine branch of the family produces clarets so distinguished (and expensive) that wine buffs whisper their names as if they were religious incantations: Château Mouton Rothschild, Château Lafite…most of us dream that Uncle George will leave us a bottle or two in his will instead of the Maserati. The natural historical branch of the family was founded by Walter, second Baron Rothschild. He donated his private collection to the Natural History Museum on his death in 1937. This is the collection to be found in his old house at Tring, in Hertfordshire, thirty miles from London, where the ornithological collections of the Zoology Department now reside, eggs and skins in their thousands. The collection of domesticated dogs on display is another kind of “museum of a museum,” a taxidermist’s Mecca, a canine compendium. Walter’s brother Charles was another dedicated natural historian who combined a successful business career with an intense interest in the taxonomy of fleas.
Miriam was Charles’ daughter, and was devoted to him. When he left his collection of fleas to the Natural History Museum, she dedicated more than twenty years to its study. Her father had committed suicide in 1923, probably because of depression brought on by suffering from encephalitis lethargica, that mysterious “sleeping sickness” that followed upon the First World War. George Hoskins and Miriam Rothschild’s great work An Illustrated Catalogue of the Rothschild Collection of Fleas (Siphonaptera) in the British Museum (Natural History) (five volumes, 1953–71) was the ultimate tribute of the talented daughter to the naturalist father. Miriam’s natural habitat was looking down a microscope, and those who said she preferred animals to humans were probably not far from the truth. She was known as the Queen Bee. Her researches showed that the reproductive cycle of the rabbit flea was tied into that of the hormonal cycles of their host. This had relevance to stemming the plague of rabbits in England in the middle of the twentieth century by the introduction of myxomatosis. She became interested in the chemistry of the pheromones that induce sexual attraction in insects. She pioneered conservation techniques on her estate at Ashton Wold, near Peterborough—leading by example, and founding the notion of “think globally, act locally.” She realized the importance of small areas like roadside verges in maintaining biodiversity, something that is now adopted by many a Wildlife Trust. Miriam carried on working even as her sight failed, right up to the end. Her last scientific contribution postdated her. When I was a young employee at the Museum she was a Trustee, and the first woman ever in that role. We all looked forward to a glimpse of her. Her battered old Rolls-Royce would glide up the ramp at the front of the Museum, and the Queen Bee would step out in some rather large black dress—but sometimes still wearing the gumboots in which she had stomped around her paddocks that morning. As my mother used to say, she didn’t give a damn. Her chauffeur was a thin man, with a pockmarked complexion, decked out in a reddish livery. He used to stand around scratching himself in a bored kind of way as if one of the samples had escaped.
Walter Rothschild atop a giant tortoise
I ought to explain some more about specimens at this point. When I went on my pioneering wanderings through the bowels of the Museum, and finally reached the entomologists, the drawers that I opened were full of pinned insects. A pin impaled each specimen through the thorax, like the stake that finished off Dracula in the many films starring Christopher Lee. This is how you fill up a collection of butterflies and beetles: you pin them down. Dozens or even hundreds can fit in a drawer. But the tiny insects we have been discussing are obviously too small for such impaling. They need a different method to preserve them for posterity. Some are preserved in spirit in small phials as whole specimens. But most of them are “prepared”—spread out on microscope slides, often dissected into several pieces, with their cuticles chemically cleared. Depending on the type of insect concerned, there may be wings laid out, or the “hairs on legs,” or the genitalia, or the mouthparts. It is a way of defying time, of turning a tiny, living thing into an archive of life. The process somehow recalls the twilight lines of T. S. Eliot in “The Love Song of J. Alfred Prufrock”: “When the evening is spread out against the sky / Like a patient etherized upon a table.” It is a moment of
existence anaesthetized or protected from decay. Aphids (greenfly) have their soft and squashy innards sucked out, and their thin outer coverings preserved, like a coat that perfectly models the body. Then a truly vast number of specimens can be stored inside a single cabinet. Parasitic wasps are minute creatures that lay their tiny eggs upon larvae of other insects, which then hatch to consume their hosts. They, too, are preserved dissected in ranks of slides, all neatly labelled at one end. Small creatures somehow encourage neatness in curation.
Insect pests often do come in small sizes: think of weevils in flour, furniture beetles with their tiny “woodworm” holes, greenfly on the roses, clothes moths in bottom drawers. A thing of small dimensions creeps in through cracks and does damage: it is “The invisible worm / That flies in the night / In the howling storm” that sickened William Blake’s rose. But the tables can be turned: some diminutive insects can be employed to positive ends. Parasitic wasps can be used to target particular pests, because they are very choosy about their victims. Natural History Museum entomologist Andrew Polaszek explained to me how this form of biological control has been used successfully to combat the depredations of certain white flies. Despite their name, these tiny flyers are not flies—they are actually miniature relatives of the aphids. They also resemble minute white moths when they infest my cabbages—though of course they aren’t moths either. But they are virus vectors: one species has been shown to carry a hundred species of virus. This is not good news for any plant that the white fly chooses to feed on. By the kind of paradoxical nomenclatural wheeze of which nature is apparently so fond, there is a black white fly called Aleurocanthus woglumi, which has been causing much damage to the orange and grapefruit crops in Trinidad. Like so many pests, this species is a stranger which has got out of control: its natural habitat is somewhere in Asia, in China or India. It lacks natural enemies outside its home territory, so it breeds without restraint on the citrus plantations of the New World. It had already made its presence known in Florida, a state that is a vast producer of orange juice. Help came in the form of a minute species of parasitic wasp (Encarsia perplexa, colour plate 11) specialized to consume this white fly species alone: like the Alien in the film of the same name, this wasp flourishes and grows inside its host’s larva, consuming it alive from within. It pops out in due course in place of the host that should have hatched all ready to infect yet more white flies. Vast numbers of the little wasp were bred up at the University of Florida at Gainsville and released on to the stricken plantations. The scheme worked well: the fear that the wasp might turn its attention to some other, wholly innocent species was not realized.
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