One morning not long ago, an American entomologist named Justin Schmidt was making his way up the winding road to the Monteverde cloud forest in Costa Rica when he spotted Parachartergus fraternus, social wasps known both for the sculptured architecture of their hives and the ferocity with which they defend them. This hive was 10 feet up a tree, and the tree angled out from an eroded bank over a gorge. Schmidt, who specializes in the study of stinging insects, got out a plastic garbage bag and shinnied up to bag the hive. "There's always a few that get out," he says, so he took the precaution of putting on his beekeeper's veil. Undeterred, the angry wasps charged his face, scootched their hind ends underneath their bodies in midair, and, from a range of four inches, squirted venom through the veil straight into his eyes. "There I was, 10 feet up a tree, holding a bag of live wasps in one hand, basically blinded with pain." He slid down the tree like Wile E. Coyote after a tête-à-tête with Road Runner—but he held onto the nest. The one thing wrong with the story is that he only got sprayed by the wasps, not stung. He has been more successful on other outings. Without ever deliberately trying to get stung (which he admits would be unnatural), he has managed to sample the stings of about 150 different insect species on six continents. (Antarctica, with no stinging insects, is not worth the trip.) Schmidt, who works with the Southwestern Biological Institute and the University of Arizona, is the world's leading authority on the nature of stinging. The subject obsesses him, not just in the field but also at his Tucson home, where one room is largely occupied with terrariums full of venomous animals behaving badly. He is coauthor of the standard text in the sting field, Insect Defenses: Adaptive Mechanisms and Strategies of Prey and Predators. He is also the creator of the Justin O. Schmidt Sting Pain Index, a guide to just how bad the ouch is, on a scale of one ("a tiny spark") to four ("You might as well just lie down and scream").
Biochemical Hackers
Insect stinging fascinates Schmidt because it constitutes a kind of high-tech warfare. Think of it this way: Your body is the computer, and stinging animals are the hackers—the dweebs and misfits that have managed to crack the biochemical code. With a little venom, they can penetrate cell membranes, manipulate neurons, convert systems of self-defense into instruments of self-destruction, alter the function of the heart, and even, in some cases, take over the central nervous system and subvert a victim's entire behavior pattern to their own needs. The toxins are so subtly attuned to biochemical nuances that pharmaceutical companies regularly study them in search of new drugs. Human tests are currently under way, for instance, using components of scorpion venom to treat brain tumors. A toxin from marine cone snails is the basis for a promising new spinal pain remedy. Stinging animals can also kill. In this country, fatal attacks by jellyfish and scorpions are rare. But according to Schmidt, about 40 people die each year from insect stings. Yellow jackets, honeybees, and fire ants—all members of the order Hymenoptera—are the usual culprits.
The Mother of All Stings
Only the females of these insect species sting, and sex—or rather reproduction—is the reason they first learned how. It started back in the Jurassic Period, in an unknown species of parasitic wasp. Such wasps commonly use their ovipositor, a pointy extension of the abdomen, to lay their eggs on living caterpillars, beetle grubs, and other hapless victims, usually at a rate of one egg per victim. Some species actually have a serrated edge on the ovipositor to saw through flesh and deposit the egg inside the body. The wasp egg hatches, and the larval wasp then feeds on its living host until it sucks it dry, or in the case of a larva inside the victim, until it is big enough to burst forth, Alien-fashion, and fly away. The intended host understandably does not like big Mama Wasp buzzing around, and it typically throws up a frenzied resistance. But at some point in the primordial struggle, the saw-blade lubricants or other fluids in the ovipositor of some wasp species became paralyzing to victims. This made life infinitely easier for the wasp, and from this eureka moment, venoms evolved to suit an immense variety of circumstances, and ovipositors adapted to function as stingers. Bees and ants eventually evolved from Mama Wasp, and at least 60,000 different species in the order Hymenoptera now possess some form of stinger. Impression fossils of a wasp from Russia show that this evolutionary flowering was already well under way more than 120 million years ago. Even now, the vast majority of stinging insects use their venom primarily to parasitize tomato hornworms, cabbage loopers, and the like. Insect stinging is thus more a blessing on humanity than a curse: If female parasitic wasps were not out there busily killing agricultural pests, we would starve. But this is all too easy to forget in a moment of pain. For us, stinging mostly means nasty encounters with bees and other social insects that have retained no trace of the parasitic lifestyle. They now sting purely to defend the hive, and they are dismayingly good at what they do. On Justin Schmidt's sting pain index, honeybees rate only a two ("like a match head that flips off and burns on your skin"). But no instrument of biological terror is quite so thoroughly understood by science.
