Wicked Bugs
Page 14
Even more mysterious, though, was their sudden disappearance. The swarms diminished in size through the turn of the century, and eventually scientists realized that they had vanished all together. The Rocky Mountain locust—the grasshopper known as Melanoplus spretus—has not been seen alive since 1902. Although other species of grasshoppers swarmed across the West during the Great Depression, they were not nearly as destructive, nor as widespread, as the Rocky Mountain locust.
Scientists now think that farmers managed to eradicate the locust by doing what they do best—farming. As they turned prairie land into cornfields and cow pastures, they destroyed the insects’ only permanent breeding grounds, a series of rich river valleys along the Rocky Mountains where the entire population returned every year to breed. Melanoplus spretus now appears to be entirely extinct—much to the relief of American farmers.
Meet the Relatives Not all grasshoppers are capable of turning into locusts. Out of eleven thousand species of grasshoppers, only a dozen or so are known for becoming locusts under pressure.
DESTRUCTIVE
FEAR NO WEEVILS
Soldiers fighting in the Civil War must have felt that they spent more time battling bugs than the enemy. From the lice that inhabited their clothes, to the mosquitoes that inflicted malaria and yellow fever, to the weevils that bored through their rations, insects were a never-ending problem. While the weevils weren’t the most dangerous insects soldiers encountered, they may well have been the mostdemoralizing.
Union soldiers carried a kind of biscuit called hardtack, made of flour, salt, and water.
It was thick, dry, and not particularly tasty, but it resisted mold as long as it didn’t get wet—which was difficult under the circumstances. Even if it didn’t come out of the package damp and moldy, hardtack was usually infested with weevils. Soldiers developed their own techniques for evicting weevils from their food, such as dunking it in coffee until the bugs floated to the top, then skimming them out with a spoon. But more often than not, bugs were simply part of the meal. One soldier said that “all the fresh meat we had came in the hard bread.” He preferred his meat cooked, he said, so he toasted the hardtack first.
Soldiers often joked that they didn’t have to carry their rations; the food was so bug-infested that it walked on its own. But behind the jokes were misery and simmering anger. On Galveston Island, in August 1863, the troops staged a mutiny over the lack of wages, the endless drills in the summer heat, and especially the “sour, dirty, weevil-eaten” cornmeal they were expected to eat.
Weevils are small herbivorous insects with elongated, downward-curving snouts. Some have changed the course of history with their destructive behavior.
GRANARY WEEVIL
Sitophilus granarius
Also known as the wheat weevil, it chews into a grain of wheat, deposits an egg there, then seals the hole with a special secretion. The larva lives inside the grain of wheat until adulthood, then it chews its way out to mate and begin the cycle again. This is the species most likely to have turned up in hardtack rations.
RICE WEEVIL
Sitophilus oryzae
In spite of its name, the rice weevil will attack not just rice, but corn, barley, rye, beans, and nuts. Originally from India, it is now found in pantries around the world, particularly in warmer climates. Like the granary weevil, it bores into stored grains to lay its eggs, making it frustratingly difficult to detect. At only two to three millimeters in length, it blends in with the grains it infests.
BOLL WEEVIL
Anthonomus grandis
Perhaps the world’s most famous weevil, this small brown creature, no longer than a fingernail, crossed the border from Mexico into the United States in 1892 and quickly went to work devouring the nation’s cotton crop. In Georgia alone, cotton production dropped from a peak of 2.8 million bales to just 600,000. In 1922, the boll weevil ate 6.2 million bales of cotton. The Great Depression came along before much progress could be made in getting the insect under control, leading some farmers to simply give up on farming and abandon their land. Other farmers took the opportunity to diversify, planting peanuts or other crops that ultimately proved more profitable—but that changed the South forever. The town of Enterprise, Alabama, even built a monument to the weevil to mark its role in pushing them to abandon cotton in favor of more profitable crops.
Since its arrival, the boll weevil has cost cotton farmers $91 billion, or over $2 million per day. A barrage of poisons were tried on the boll weevil, including a mixture of molasses and arsenic that farmers could brew themselves, a dusting of calcium arsenate, and eventually DDT and other post–World War II insecticides. The weevils developed resistance to those chemicals even before they were banned. Since 1980, the U.S. Department of Agriculture has undertaken a nationwide boll weevil eradication program that involves every acre of cotton planted in the United States—fifteen million acres in all. Using integrated pest management techniques, the weevil has been eliminated from 87 percent of America’s cotton fields, and growers have reduced their pesticide use by at least half.
PECAN WEEVIL
Curculio caryae
A pest of pecan and hickory trees, this weevil bores into nuts and deposits its eggs there. The larvae eat the inside of the nut as they mature, and people who have the misfortune to crack one of these nuts open will be treated to the sight of a fleshy white grub devouring the kernel.
BLACK VINE WEEVIL
Otiorhynchus sulcatus
This enemy of ornamental gardens feeds on plants like wisteria, rhododendron, camellia, and yew. The adults are all females; no males are needed for reproduction. They lay their eggs in the roots of plants, and the larvae devour the roots. The adults feed on the leaves, leaving telltale notches around the edge.
Civil War soldiers often joked that they didn’t have to carry their rations; the food was so bug-infested that it walked on its own.
DANGEROUS
Sand Fly
PHLEBOTOMUS SP.
British television personality Ben Fogle has had plenty of opportunities to be exposed to dreadful exotic diseases. The host of several BBC adventure programs has been marooned on a remote island in the Outer Hebrides, crossed the Atlantic in a rowboat, and raced across the Sahara on foot. He was, it seemed, invincible—until, at the age of thirty-four, he met the sand fly.
This tiny, wheat-colored fly lives for only two weeks as an adult. The females require blood meals in order to nurture their eggs, and while their bites may be almost painless, they can be extremely annoying. In sand fly–infested areas, people often find themselves in the middle of a swarm. This happens because the males, who don’t bite, hang around warm-blooded hosts waiting for a female to show up for dinner. So what may feel like an attack is actually an elaborate mating ritual that just happens to have a food source—you—at the center of it. Entomologists call this swarm a mating lek.
SIZE:
Up to 3 mm
FAMILY:
Psychodidae
HABITAT:
Forests, wooded wetlands, and sandy areas near water sources in tropical and subtropical climates
DISTRIBUTION:
Phlebotomus species are found in the Middle East, southern parts of Europe, as well as parts of Asia and Africa. Sand flies in the genus Lutzomyia, which also transmit leishmaniasis, are found in many parts of Latin America.
When a female bites, she first injects her mouthparts into the skin, using her toothed mandibles like scissors so that she can create a pool of blood to drink, and then injects an anticlotting substance that allows her to enjoy her meal a little longer. The flies transmit several diseases, but perhaps the best known is leishmaniasis. This is the disease that nearly killed Ben Fogle after an expedition through Peru.
The sand fly is such a problem in the Middle East that troops stationed there refer to the wounds as “Baghdad boil.”
Fogle began to feel some malaria-like symptoms while he was in the jungle—dizziness, headaches, lack of appetit
e—but he continued filming, then returned to London to train for an expedition to the South Pole. He collapsed during training and was bedridden for weeks while doctors tried to find the answer. Tests for malaria and other, better-known diseases were negative. It wasn’t until an ugly sore erupted on his arm that he finally had a clue.
Leishmaniasis is caused by a parasitic protozoa transmitted from other animals to humans via the bite of the sand fly. The disease takes different forms: cutaneous leishmaniasis, which causes a sore that can take months or even a year to heal, and visceral leishmaniasis, a potentially fatal version in which the protozoa infest the internal organs. Another form, mucocutaneous leishmaniasis, causes ulcers and long-lasting damage around the nose and mouth. Fogle had the misfortune to be infected with the more dangerous visceral form of the disease. He required long-term intravenous treatment, but he’s now back at work writing, traveling, and filming new shows.
The less harmful cutaneous form of the disease is such a problem in the Middle East that troops stationed there refer to the wounds as “Baghdad boil.” In 1991, United States soldiers returning from the Gulf War were asked to not donate blood for two years due to the possibility of transmitting leishmaniasis. There was another outbreak in 2003; although military officials issued warnings about the threat, bug sprays and bed nets were in short supply. It is estimated that over two thousand troops have been infected, but the number could be significantly higher now that troops are treated in the field rather than flown to military hospitals where statistics are kept. Unfortunately, doctors in the United States may not recognize the skin lesions since the disease is not common here—and that could lead to misdiagnoses and delays in treatment for returning soldiers.
Around the world, an estimated 1.5 million people become infected with the cutaneous form of the disease every year, and half a million are diagnosed with the visceral form. The drugs used to treat the disease are themselves quite serious and require close monitoring. Although research on a vaccine is underway, the only way to prevent the disease right now is to avoid the sand fly—which, in spite of its name, is found not just in desert climates, but throughout the tropics and subtropics.
Meet the Relatives There are dozens of species of these bloodsucking flies that transmit disease, but the insect most Americans refer to as a sand fly is actually a more distant relative called a biting midge.
PAINFUL
Scabies Mite
SARCOPTES SCABIEI VAR. HOMINIS
Dr. Francesco Carlo Antommarchi served as one of Napoleon Bonaparte’s last physicians during his exile to St. Helena. His difficult and demanding patient had suffered from a number of ailments over the years, including digestive problems, liver disease, and a mysterious rash. On October 31, 1819, just a year and a half before Napoleon’s death, the doctor recorded this bizarre exchange:
“The Emperor was uneasy and agitated: I advised him to take some calming medicine which I pointed out to him. ‘Thanks, Doctor,’ said he; ‘I have something better than your pharmacy. The moment approaches, I feel when Nature will relieve herself.’ In saying this he threw himself upon a chair, and seizing his left thigh, tore it open with a kind of eager delight. His scars opened anew, and the blood gushed out. ‘I told you so, Doctor; I am now better. I have my periods of crisis, and when they occur I am saved.’”
SIZE:
Up to 0.45 mm
FAMILY:
Sarcoptidae
HABITAT:
Found on or very near its host
DISTRIBUTION:
Worldwide
Antommarchi was not the first to observe Napoleon tearing apart his own skin. One of his servants wrote that “on several occasions I saw him dig his nails into his thigh so vehemently that the blood came.” He was sometimes so covered in blood during military campaigns that his soldiers thought he had been wounded, when in fact he was just raw from scratching. We may never know exactly what drove Napoleon into such a frenzy, but at least one doctor who treated him diagnosed the rash as scabies.
Napoleon believed it was that moment that he “imbibed the infection ot the itch,” from a dead soldier in the battlefield.
Although it was not well understood at the time, the scabies mite certainly afflicted troops during the Napoleonic wars and virtually all wars since. Crowded conditions, the necessity of wearing the same clothing day after day without washing, and mass migrations of poor people during wartime all contribute to the spread of scabies. There were some attempts made during the late 1600s to persuade the medical community that scabies was caused by a parasite, but those ideas were largely ignored. Napoleon’s doctors would have most likely believed that scabies was caused by an imbalance of the “humours.”
What Napoleon did understand was that scabies was infectious. He described an incident early in his career that begin his long history of skin troubles. During the siege of Toulon in 1793, a gunner was shot while loading a cannon, so Napoleon stepped in and took his place. Both the dead soldier and his equipment were covered in sweat from the excitement of the battle; Napoleon believed that it was at that moment that he “imbibed the infection of the itch, with which the soldier was covered.”
By 1865, some decades after Napoleon’s death, it was finally understood that scabies was caused by the actions of a nearly invisible mite. An adult female burrows into the skin, usually around the hands and wrists, and lays a few eggs every day. The eggs hatch and the larvae move into an upper layer of the skin, where they form tiny dwellings called molting pouches. They molt into nymphs and then into adult mites, who will mate just once during their short lives, all the while occupying this space under the skin. Once pregnant, the females leave their burrows at last, and walk along their host’s body until they find another suitable location to start a new family. In all, a scabies mite lives for one to two months, spending almost all that time under the skin of its host.
People who are infested with scabies might not experience any symptoms at all for the first month or two. Over time, however, they develop a severe reaction to the mites themselves, not to mention the waste products left under the skin. Sometimes a rash spreads all over the abdomen, shoulders, and backside, even when no mites can be found there. Because the mite can live a few days away from its host, it is theoretically possible to transmit scabies through clothing, bedsheets, and toys, although the most common means of transmission is skin-to-skin contact. While Napoleon suffered his whole life from a probable scabies infection, doctors today can treat the condition with a topical cream.
Meet the Relatives A variety of scabies mites infest humans, wild animals, and domesticated animals. The mite Sarcoptes scabiei canis causes a type of mange in dogs known as sarcoptic mange.
PAINFUL
WHAT’S EATING YOU?
Scabies mites weren’t the only parasites to torture Napoleon. General Bonaparte marched into Russia with over half a million men in 1812 and left, defeated, with only a few thousand. What happened? Napoleon himself blamed the cold winter, but scientists now think that it was a tiny, wingless, flattened insect that brought the world’s mightiest army to its knees. During their march the soldiers were forced to scrounge food and shelter from peasants in the Polish and Russian countryside, and from those impoverished people they picked up a nasty case of body lice. One soldier wrote that he awoke to a sensation of “unbearable tingling . . . and to my horror discovered that I was covered with vermin!” He jumped up and threw his clothes into the fire, a move he surely came to regret as winter approached and supplies grew scarce.
But it wasn’t just “unbearable tingling” that led to Napoleon’s defeat. Body lice carry typhus, trench fever, and any number of other nasty diseases that can decimate an army. Napoleon’s few surviving troops were so sick that they had no choice but to retreat from Russia, a defeat that marked the beginning of the end of his brilliant military career.
In 1919, at the height of the Russian Civil War, typhus was again rampant as a result of the poverty, crowded conditio
ns, and warfare that breed body lice, causing Lenin to say that “Either socialism will defeat the louse, or the louse will defeat socialism.”
Of the four thousand species of lice around the world, humans lay claim to only three: body lice, head lice, and pubic lice. These three species feed exclusively on people, where they each occupy distinct niches in the ecosystem of the human body. This fact recently led evolutionary biologists to some startling facts about our history. Head lice date back 7 million years, when humans and chimpanzees shared a common ancestor. Body lice evolved from head lice about 107,000 years ago, around the time humans started wearing clothing. Pubic lice, however, are more closely related to gorilla lice—and were transferred to humans through some sort of intimate physical contact with gorillas, the precise details of which remain a mystery.
BODY LICE
Pediculus humanus humanus (syn. Pediculus humanus corporis)
Body lice are, fortunately, unfamiliar to most people. The creatures have evolved to lay eggs in the seams and linings of clothing, not on the body itself. For this reason they’re only found among homeless or impoverished people who must wear the same clothes for weeks at a time without washing. The eggs hatch in response to body heat, so clothes that are worn constantly provide the best breeding ground. The newly emerged nymphs migrate to the skin and must feed within a few hours to survive. Over the next week they grow into a full adult and live for a few weeks more, feeding on human blood the whole time. In the most severe cases, up to thirty thousand body lice have been reported on one individual. Even without the possibility of disease transmission, simply being plagued by these tiny bloodsuckers can be dangerous.