by Amy Stewart
SAN BUSHMEN
According to Hendrik Jacob Wikar, a Swedish-born soldier traveling through South Africa in the late 1700s, there was a poisonous worm that could be ground into a powder, mixed with plant juices, and applied to the tips of arrows. Explorers coming after him realized that he was probably referring to the larvae of several species of African leaf beetle, Diamphidia sp., whose hemolymph — bug blood — contains a toxin that causes paralysis. The adult beetle resembles a yellow and black ladybug, while the larvae are large, flat, flesh-colored grubs. They are found on one particular small shrub in the Commiphora genus native to South Africa and widely used by the San people. Another leaf beetle, Polyclada flexuosa, is sometimes used as well.
A carabid or ground beetle, Lebistina sp., related to the bombardier beetle, is also used in the poison arrows of San hunters. This beetle is actually a parasite of the African leaf beetle, so they are often found together. The juices of these larvae are sometimes squeezed directly onto the tip of a poisoned arrow and then dried over a fire; they can also be mixed with plant sap or tree gum, which acts like glue to hold the poison on the arrow, or they can be ground into a powder and then mixed with the juices of plants.
Although these poisons can kill a small animal like a rabbit within a few minutes, it takes several days to bring down a large animal like a giraffe, which means that the hunters often spend days tracking the animal and waiting for it to die. But they do work eventually. Thomas R. Fraser, a late-nineteenth-century expert in pharmacology, wrote that these arrow poisons were strong enough to “drive any unfortunate raving mad before he dies in agony.”
ALEUT
Native people from Alaska’s Aleutian Islands made a mixture of a poisonous plants (aconitum, or monkshood), rotten animal brains and fat, and an unspecified poisonous worm or caterpillar.
HAVASUPAI
These tribespeople, who once lived in and around the Grand Canyon, made use of what was described only as a “small black biting bug,” along with scorpions, centipedes, and red ants, to make their arrow poisons. The Jova tribe in northern Mexico made a similar cocktail of rotten cow livers, rattlesnake venom, centipedes, scorpions, and poisonous plants.
APACHE
One tribal member described an arrow poison recipe that involved hanging up pieces of a cow’s stomach until it rotted, then holding wasps against it so that they would be forced to sting the meat. It would then be mashed together with blood and cactus spines and applied to the tips of arrows.
POMO
This California tribe was described as using a mixture of rattlesnake blood, spiders, bees, ants, and scorpions, all crushed together to form a poison that could be applied to arrows and then shot over the homes of enemies as a kind of bad-luck curse.
YAVAPAI
This southwestern tribe had perhaps the most complex recipe for poisoned arrows: A deer liver, stuffed with spiders, tarantulas, and rattlesnakes, would be buried and then a fire would be burned on top of it. It would then be dug up and allowed to rot, before finally being made into a paste. One anthropologist recorded the story of a soldier who experienced one of those arrows firsthand. It took only a few days to kill him. (The use of rotten meat, it should be noted, might have introduced deadly bacteria into the victim’s bloodstream, along with the poison.)
These arrow poisons were strong enough to “drive any unfortunate raving mad before he dies in agony.”
DEADLY
Mosquito
ANOPHELES SP.
On July 10, 1783, just as the Revolutionary War was coming to an end, George Washington wrote to his nephew that “Mrs. Washington has had three of the Ague & fever & is much with it — the better, having prevented the fit yesterday by a plentiful application of the Bark — she is too indisposed to write to you.”
SIZE:
Wing length 3 mm
FAMILY:
Culicidae
HABITAT:
Varies widely, but usually found around bodies of water, from lakes to marshes to isolated pools
DISTRIBUTION:
Found in tropical, subtropical, and some temperate climates worldwide
The “Ague & fever” that the future first president of the United States was referring to was malaria, a disease that had plagued him since he was a teenager and also infected his wife. He suffered several bouts of it over the years, along with smallpox, typhoid fever, pneumonia, and influenza. And although the treatment for malaria — quinine, extracted from the bark of the South American cinchona tree — was already in use in Europe, the Washingtons did not have access to it until later in life. Unfortunately, the president took so much of the drug that it caused severe hearing loss during the second year of his term — a known side effect of quinine toxicity.
Malaria has been called our forever enemy because it predates humans, as demonstrated by tests on mosquitoes preserved in amber from thirty million years ago. The earliest medical texts made reference to a malarial fever, and some even suggested that an insect bite could be the cause. But the word malaria, from the Italian word for “bad air,” suggests the commonly held belief that malaria was simply present in the air.
As we now know, mosquitoes are to blame. They transmit not just malaria but dengue fever, yellow fever, Rift Valley fever, and about a hundred other human diseases. Roughly one in five of all insect-transmitted diseases come from mosquitoes, making them the world’s most deadly insect. Malaria is believed to have killed more people than all wars combined.
Malaria is caused by a parasite in the genus Plasmodium. Female mosquitoes, not males, feed on blood. They must first become infected themselves by feeding on a host and taking up both male and female plasmodia, which then reproduce in the mosquito’s body and make their way to the salivary glands. Because mosquitoes live only a few weeks, they may not survive long enough for this to happen. But if it does, and they then feed on someone else, the disease cycle continues. They inject saliva into their victim, where it acts as an anticoagulant. If enough parasites are present in the mosquito’s saliva, the victim may become infected — but it is possible to be bitten by an infected mosquito and not get malaria.
Mosquitoes are attracted to their hosts by carbon dioxide, lactic acid, and octenol, components found in human sweat and breath. They also sense heat and humidity around a body. They like dark colors, and they seem to be drawn to people who have been exercising. A French research team recently discovered that mosquitoes are more attracted to beer drinkers. In Rangoon, Myanmar, residents can get as many as eighty thousand bites per year. In northern Canada, when mosquito populations are high, people can get bitten as many as 280 to 300 times per minute. At this rate, it would take only ninety minutes to drain half the blood from a human body.
Today 41 percent of the world’s population lives in an area where malaria can be caught. There are nearly five hundred million cases worldwide, and every year over one million people die, most of them young children in sub-Saharan Africa. Experts estimate that controlling malaria worldwide would cost $3 billion. Bed nets play a critical role in protecting people at night when mosquitoes are active, and prophylactic drugs like quinine are also an important strategy in preventing the disease. Currently there is no vaccine.
Malaria did have a brief starring role as a possible treatment for another disease. In 1927 Julius Wagner-Jauregg won the Nobel Prize for coming up with the idea of therapeutic malaria, the practice of deliberately infecting a patient with malaria to cause a fever high enough to kill some infections. He used this technique on late-stage syphilis patients. Once they were cured of syphilis, he administered quinine to treat the malaria. Fortunately, penicillin came along by the 1940s, putting an end to what must have been a miserable way to fight disease.
Meet the Relatives All mosquitoes are found in the family Culicidae. There are roughly 3,000 species, 150 of which live in North America.
DESTRUCTIVE
Mountain Pine Beetle
DENDROCTONUS PONDEROSAE
In an a
rticle titled “What the Depredation of Insects Costs Us,” the New York Times declared that the combined value of everything destroyed by insects would cost us the equivalent of our entire federal budget, and those of several European countries as well. The mountain pine beetle was one of several that “left a trail of ruin” through America’s forests by burrowing under the bark, chewing tunnels through the wood, and “leaving millions of dollars’ worth of timber in a decaying and useless condition.”
SIZE:
3–8 mm
FAMILY:
Curculionidae
HABITAT:
Pine forests
DISTRIBUTION:
Found throughout North America, from New Mexico, Colorado, Wyoming, and Montana, to the West Coast. In Canada, found throughout British Columbia and parts of Alberta.
When did this alarming news reach the American public? 1907. By the 1930s, a full-scale war was underway in the American West, with Congress appropriating millions of dollars to study and fight the bug that was devouring the forests. But the efforts of Congress were no match for the mountain pine beetle: by the 1980s, the Times again reported that the insect was ravaging America’s forests, taking out 3.4 million acres in the American West. And 2009 was even worse, with 6.5 million acres destroyed in the United States, and 35 million acres in British Columbia — an area roughly the size of New York state.
The mountain pine beetle, a creature no bigger than a grain of rice, burrows into the bark of a pine tree until it reaches living tissue. There she eats and lays her eggs, sending out a pheromone to other beetles to let them know that she’s found a good tree. The tree tries to fight back, excreting a sticky resin that can kill the beetles, but usually that defense isn’t enough. As the insects burrow into the tree, they transmit a disease called blue stain fungi that essentially clogs the tree’s tissue, making it impossible to transport water up to the leaf canopy.
The larvae spend the winter underneath the bark, keeping themselves warm by turning carbohydrates into glycerol, which acts as a kind of antifreeze to keep them from freezing to death. In the spring, the glycerol is converted back to carbohydrates and serves as an energy source while they pupate under the bark. They emerge as adults in July, mate briefly, and complete the cycle. Mountain pine beetles live for a year, spending all but a few days of that time under the bark of a tree.
In a typical forest, the beetles will start by attacking old, weak, or diseased trees. By going after the older trees first, the beetles actually help “recycle” aged trees and make room for the next generation. But many foresters agree that decades of fire suppression have led to forests with dense populations of older trees, rather than a diverse mix of generations. Now all these older trees are under attack at once. A long, deep freeze might kill off the larvae overwintering under the bark, but recent warmer winters have made it easy for large populations to survive and reproduce.
The devastation brought on by the mountain pine beetle is easy to see from the air. Diseased trees turn red as they die, making what once was a vibrant green pine forest look more like the New England woods in the fall. Unfortunately, there is no good way to control the beetle: natural predators like woodpeckers play a limited role but can’t stop an outbreak; chemical controls are cost-prohibitive; and time-consuming treatments like peeling the bark away to expose (and kill) the larvae are not practical on a large scale. Foresters have focused instead on prevention, including thinning trees and allowing some natural fires to encourage an age-diverse forest. The question remains of what to do with the diseased trees. Some experts have suggested turning them into wood chips that can be used to make ethanol or pressing them into pellets that can fuel stoves. In Vancouver, where the beetle has hit hardest, the 2010 Winter Olympics arena featured a roof made from over a million board feet of pine beetle–infested wood.
Meet the Relatives Related to a wide range of other destructive bark beetles and weevils, including the southern pine beetle (Dendroctonus frontalis), found throughout Central America and the southern United States, and the European spruce bark beetle (Ips typographus), which has devastated spruce forests in central Europe and Scandanavia.
DESTRUCTIVE
Nightcrawler
LUMBRICUS TERRESTRIS
By the 1990s, scientists at the University of Minnesota had come to expect questions from the public about the strange changes to their forests. Something was happening, people said. The young understory plants — the ferns and wildflowers — were disappearing. There were fewer trees, and almost no young trees. When the snow melted in spring, there was only bare dirt, not the carpet of greenery people expected to see. It was as if the forest had stopped renewing itself. People would call the forestry department looking for answers, but the scientists were just as puzzled.
SIZE:
25 cm
FAMILY:
Lumbricidae
HABITAT:
Rich, moist soils
DISTRIBUTION:
Worldwide
Then one of the researchers, a doctoral student named Cindy Hale, read an article about the forests in New York. “It mentioned, in kind of an offhand way, that increases in earthworm populations might be causing changes in understory plants,” she said. “That’s when it finally occurred to us to go out into the forest with a shovel and dig.”
It would come as no surprise to most people that what they found was earthworms. This shouldn’t be cause for alarm — after all, earthworms are good for the soil. They improve drainage, they move nutrients around, they deposit their rich castings around plant roots, and they help break down organic matter. Farmers and gardeners brag about their earthworm populations as indicators of healthy soil. But, as the Minnesota team was about to find out, earthworms are not always as beneficial as people believe them to be. The worms turned out to be a European species. Lumbricus terrestris, better known as the nightcrawler, was the largest and easiest to identify. Lumbricus rubellus, a smaller species sometimes called a red worm, was also abundant in the soil. In all, they have found fifteen nonnative species living in the forest floor.
Earthworms are not always as beneficial as people believe them to be.
Because Minnesota was covered by glaciers during the last Ice Age, its forests have evolved without any native earthworms. Native North American worms can be found throughout much of the country, but those northernmost portions were absolutely free of worms — until European species arrived.
European worms came to the United States with settlers in potted plants, in soil used as ship’s ballast, and embedded in wagon wheels and the hooves of cattle. They moved across the country as quickly as the settlers themselves did. Today the earthworm population in a typical American backyard is likely to be made up mostly of European worms. In most gardens, these worms do only good — but that was not the case in Minnesota.
By monitoring test plots, Hale and her team were able to demonstrate that European worms could completely devour the layer of leaves that fell every autumn. Under normal circumstances, the leaves would remain on the ground year after year, forming a spongy duff layer that native plants required in order to germinate and grow. But rotten leaves are like candy to the night-crawler. In areas with the heaviest infestation, the duff layer was gone entirely and replaced by a thin blanket of earthworm castings. The native Minnesota trees and wildflowers simply couldn’t survive in it.
Solomon’s seal, large-flowered bellwort, wild sarsaparilla, and early meadow rue are just some of the plants that are disappearing. Sugar maples, red oaks, and other native trees and shrubs also can’t get established in this unfamiliar soil. And as people come into the forests around the Great Lakes, bringing with them live worms for fishing bait, soil for fill dirt, or even tires caked in mud, the earthworms continue to spread. Even building a golf course near a forest can pose a risk, as acres and acres of sod are installed, complete with the earthworms that live in it.
What can be done to stop the invasion of European worms into forests that ev
olved without them? They can’t be evicted; it’s not possible to put up a fence to keep earthworms out. Hale and her team found that excluding deer from the forest can make a difference, because the few plants that do manage to survive get eaten by deer. They hope to slow the spread of the worms by discouraging the use of worms as fishing bait and by educating people about the potential hazards of the gardener’s best friend.
Meet the Relatives The red worm, Lumbricus rubellus, is often found in compost piles, as is the red wiggler, Eisenia fetida.
DANGEROUS
THE ENEMY WITHIN
German physician Friedrich Küchenmeister published a book in 1857 on human parasites in which he described the distress people find themselves in when they discover tapeworms attempting to leave their bodies. “The passage of the segments without feces is a constant annoyance to the patient,” he wrote. “The proglottids [tapeworm segments] adhering to the naked body in the trousers, or under the petticoats, being disagreeable, from their clammy coldness, disturb the patients greatly; and women especially are afraid lest the proglottids should fall unperceived upon the ground when they are walking or standing.”
But parasitic worms do more than embarrass ladies in petticoats. And often, they are helped along by some other creatures that play a critical role in getting the worms into our bodies in the first place.
PORK TAPEWORM
Taenia solium
In the fall of 2008, a thirty-seven-year-old Arizona woman was in for the most frightening day of her life. She was being wheeled into surgery to have a tumor removed from deep inside her brain. It was a risky procedure, but she had little choice: her left arm was numb, she had lost her balance, and she was beginning to have difficulty swallowing. The tumor had to come out.
