I have been attacked by animals for thirty years. Working at a veterinary clinic in high school, I learned the skill of keeping snarling dogs at bay with a squeegee and the art of restraining injured cats. Later, in college research laboratories, I encountered the occasional frightened rat willing to use its yellowed incisors in self-defense. The mice seemed less threatening, but were quicker to draw blood if carelessly handled.

But I was unprepared for the unmitigated ferocity of the Gryllacrididae — insects that look like a cross between a cricket and a grasshopper. My research as a professor at the University of Wyoming had focused on grasshoppers, and I had the opportunity to spend a sabbatical leave in Australia working with their relatives. While grasshoppers can be feisty, kicking and struggling valiantly when held, gryllacridids are fierce. Lifting their wings to appear larger and thumping their abdomen against the ground like a war drum, they launch themselves at any intruder. Their gaping, sickle-shaped mandibles leave no doubt that they intend to inflict as much damage as possible, and the largest species can leave a deep gash in a person’s hand.

Gryllacridids attack in order to live. The smallest of these insects are no larger than a pencil stub, while the largest species are meatier than a man’s thumb. These creatures lack standard insect defenses — they have no stench, toxin, or sting. Given their bite-sized morphology and their lack of chemical protection, gryllacridids make tempting hors d’oeuvres for various predators. The insects’ primary defense is a set of characteristics that evolved to help them avoid such a fate by escaping detection. In coloring they tend toward drab, earthy shades. A row of pinned specimens in a museum drawer might well match a standard selection of men’s shoes. Their nests, whether subterranean burrows or mats of dried leaves, are invisible during the light of day. And finally, gryllacridids are strictly nocturnal, avoiding the visually oriented birds that constitute the primary predators of many insects. There are, however, plenty of nocturnal hunters seeking a midnight snack. So, when stealth fails and a gryllacridid perceives that it is faced with imminent death, it unleashes a maniacal display of mandible-gnashing, abdomen-thumping, wing-flapping ferocity. These savage creatures gave me ample opportunity to ponder the nature of violence.

Starting a new line of study in a novel place reminded me of my first days of graduate school a dozen years earlier. Dr. Jeff LaFage taught my graduate course in insect behavior at Louisiana State University with passion and intensity. He was a demanding and kind teacher, a true scholar and Renaissance man — studying the evolution of termite sociality, collecting Tiffany glass, and hosting a Baroque music program on public radio. He was unable to harm a fly without reason, but when he peered over the wire rims of glasses perched menacingly on his nose, a student who had failed to read the assigned paper or otherwise prepare for the semiweekly grilling cringed. Loathing pretense, he insisted on being called Jeff rather than Doctor LaFage, but he was one of the few academics who evinced the original meaning of the honorific title, meaning “to teach.” And so in my mind he remains Dr. LaFage.

Through the fall semester of 1983, Dr. LaFage revealed to us the ways of insects: the wonders of territoriality, the characteristics of communication, the qualities of sociality, and the origins of aggression. He would often use imaginative ecological and evolutionary scenarios to set up a series of Socratic questions that would elicit from us the answers about the complex origins of behavior.

Behavior, Dr. LaFage explained, is a function of how an animal perceives itself and the environment, as constrained by evolution and experience. Insects rely heavily on instinct, which serves them well. For example, many insects respond to a sudden surge of carbon dioxide, a sure indication that a large mammal is nearby. For mosquitoes this gas is a chemical dinner bell. But a huff of breath on a flower head induces thrips to hastily abandon their refuge. Like a swarm of living commas, they evacuate rather than risk being consumed by a lumbering grazer oblivious to their presence. Similarly, many social insects such as bees and ants rush from their nests when carbon dioxide pours in, but theirs is a charge rather than a retreat: the soldiers deploy to attack whatever creature has its face close enough to generate the chemical alarm.

For a man of such a gentle, albeit intense, demeanor, Dr. LaFage seemed to relish his review of the insectan arsenal. These creatures have mouthparts variously adapted for crushing, dismembering, slicing, and piercing. The most remarkable structures are those whose original function was co-opted for assault. In colonies of ants, bees, and wasps, only the queen reproduces; the other females have no use of their reproductive tracts. In this celibate caste, structures for depositing eggs gave way to stinging barbs, and cells that formerly produced lubricating secretions during egg-laying became poison glands. Organs once used for perpetuating life evolved into structures for killing.

But social species with the capacity to kill one another have also evolved sophisticated means of communicating relatedness and submission. Ants, bees, and termites identify nest mates by chemical cues. Only odd-smelling intruders are quickly set upon and stung mercilessly or torn to shreds. Among nonsocial insects, there are no constraints on killing. If a hungry grasshopper stumbles upon a recently molted comrade it will devour the helpless creature.

Dr. LaFage made clear that the balance sheet of evolution guaranteed that the genetic or energetic cost of violent behavior was inevitably offset by the potential benefits that it might yield. The ferocity with which the bees defend their hive arises from a genetic quirk ensuring that the workers are all intimately related sisters, sharing more genetic similarity with one another than with their mother. As a consequence, their willingness to die for the collective ensures a continued production of sisters and thereby genetic facsimiles of themselves.

Dr. LaFage was a bioeconomic hardliner. The currency of evolution is the gene: the more copies of you, the richer you are. When he spoke of his daughters, the tender tone belied his evolutionary dogmatism, but when it came to insects he maintained strict scientific objectivity. He brooked no sympathy for the worker bee eviscerating herself as the inevitable result of stinging to defend her colony. This suicidal creature was simply placing an unconsciously calculated bet with a well-established genetic payoff — if the queen is killed then the biological factory producing more sisters is destroyed. For most creatures, only one’s own life takes on this value, which explains — at least in part — why predators have only a 10 percent success in securing a meal following an attack. If the predator fails, it goes hungry. If the prey fails, it dies. Dr. LaFage rattled off a litany of extreme, last-ditch efforts used by insects to escape the grip of their predators: beetles that squeak or bleed spontaneously, moths that flash hind wings with owl-like eyespots, and crane flies that sacrifice still-twitching legs. When the cost is your life, whether corporeal or genetic, the nothing-to-lose approach becomes viable.

Gryllacridids are extremely difficult to observe in their natural habitats. I spent hours in the bush searching for these creatures with a headlamp, under the tutelage of one of Australia’s finest entomologists. Even with his instructions, I failed to see a single gryllacridid in the wild. More recently, a graduate student in Western Australia managed to track individuals of two species over several nights. His dissertation documented the complex homing behaviors of these insects, including their capacity to use dimly illuminated features of the landscape as navigational beacons. But he did not observe any encounters between individuals. It seems that gryllacridids are fiercely territorial, having evolved the rudiments of a primitive social system that minimizes the risk of conflicts through the avoidance of their own kind.

While the young may aggregate in tight groups, presumably to pool their defenses against larger predators, adult gryllacridids lead isolated lives, seeking one another’s company only for mating. The solitary adults forage in territories carved from the harsh Australian outback. They exhibit a range of feeding habits but may be typified as nocturnal scavengers and opportunistic predators. The formidable mandibles of these insects are well adapted for crushing seeds and dismantling exoskeletons — including those of their own relatives. The violence of these reclusive insects is bounded only by their physical capacity to inflict harm. In the laboratory, gryllacridids must be housed separately to prevent them from killing each other.

Part of my laboratory research in Australia involved collecting the silk that the gryllacridids produce to line their burrows or bind their leafy nests. In the wild, the smell of the silk enables an individual to relocate its nest at the end of a night’s foraging. In the lab, each insect was provided with an index card “tent” that served as a nest-building site. Within twenty-four hours, it had constructed a rudimentary matrix of snow-white silk extruded from its salivary glands, and with a second night’s work, it had woven a dense tangle of threads to impede the intrusion of predators. Before collecting this silk for chemical analysis, I used a thin glass probe to harass the tent maker into abandoning its nest, sometimes resorting to gently shoving recalcitrant insects out of their homes. In response to disturbance, one individual drummed its abdomen against the floor of the tent in a threatening display of impending violence. When I tried pushing this creature from its nest, the insect crushed the probe between its mandibles — the equivalent of snapping a matchstick.

My laboratory confrontations mimicked predator-prey encounters. The insect’s initial strategy upon being discovered was to retreat into its burrow or nest. Only with continued provocation or if flushed from its refuge did it switch from retreat to attack. Some species of gryllacridids had a very high threshold for aggression, resorting to attack only when driven into the open. Others rapidly switched from defensive withdrawal to unabashed assault.

Once engaged, the gryllacridids pressed the attack with reckless abandon. For these creatures, there was no half-hearted display of aggression, no gradual escalation of hostility. Moreover, they appeared utterly incapable of tempering their rage in proportion to the size of the intruder and the corresponding likelihood that such ferocity would be effective. While the largest species could readily draw blood, the smallest could not manage to pinch a bit of skin between their mandibles. Nonetheless, a cricket-sized individual would posture menacingly and snap at any object within range, even if it was a thousand times bigger than the insect itself. When a large individual became aggressive, the only way to handle it was to place the entire cage in the refrigerator for fifteen minutes. When the insect was immobilized in cold-stupor, I could move it into a fresh cage.

After months of working with gryllacridids, I came to understand some of what it means to be such a creature. I valued these insects as marvels of evolution — exemplars of wildness and ferocity — but also as teachers of life’s harsh lessons. How the will to live becomes a willingness to kill was a phenomenon I encountered daily. I couldn’t say that if I were a gryllacridid that I’d have acted any differently. I could say, however, that I regretted that they were unable to habituate to me. Their fear made both our lives more difficult.

One morning not long before I was to leave Australia, I injured one of the larger gryllacridids. The creature had been engaged in a wildly aggressive display, simultaneously flaring its wings and gnashing its mandibles. In the course of this frenzy, it had managed to climb to the edge of the cage to press its attack. Setting the lid down too fast, I accidentally pinned the insect against the top edge of the cage, where it thrashed and twisted. The force of the lid ruptured the tender abdominal membrane. The insect fell back into its container, and when the cage lid effected my disappearance from the scene, it calmly assessed the situation. A globule of yellow-streaked fat oozed through the gaping wound. It then curled its head down toward the leaking viscera and proceeded to consume its own entrails.

My heart sank — and with this I knew that I’d violated the scientist’s dictum of objectivity. I loved these wild animals, not with the sort of conditional affection that we have for organisms that can return our warmth but with a sort of deep empathy without pity. For we ultimately shared a defining reality: the capacity for animate relationality — for striking out in fear, attacking in anger, and writhing in pain. I believed that I finally understood what Walt Whitman meant in describing animals in Leaves of Grass: “So they show their relations to me and I accept them / They bring me tokens of myself, they evince them plainly in their possession.”

As the gryllacridid cannibalized itself, I tried to rationalize away my feeling of empathetic horror. Physiologists maintain that while insects may be pained by acute pressure, once the body wall is ruptured there appears to be no persistent tenderness. So it was that Dr. LaFage admonished us to avoid subjectivity — not all organisms process sensations in the same way. Their world is not ours. Pain, he said, is cognitive experience, not merely sensation. We cannot know what another animal experiences. Dr. LaFage would not countenance any latent anthropomorphic tendencies in his students. My feeling about what I’d done to the mangled gryllacridid did not reflect my training as a researcher. Nor did it mirror the insect’s likely reaction were I the one who had been crushed. Rather, my response was essentially that of a poetic scientist, a compassionate human. As empathetic creatures we cannot stop ourselves from imagining the pain of other sentient beings.

The year after I left Louisiana and came to Wyoming as a freshly minted PhD, Dr. LaFage entertained a visiting scientist in the French Quarter of New Orleans. He was escorting this female colleague when a mugger grabbed her purse. The woman became tangled in the strap, and Dr. LaFage stepped between them and said, “Don’t hurt her, you can have the purse.” I can picture him doing this, with the soothing confidence of a man who knows the nature of violence. I have even imagined the setting: the grimy street littered with the refuse of bars and clubs contrasting with the elegant ironwork on the balconies overhead; the sultry heat hanging limp like Spanish moss; the blended odors of wetness — sweat trickling down the small of a back, fetid water pooled in gutters, and a whiff of urine from an alley. What I can’t imagine is the next moment: the young man drew a gun and fired point-blank.

Dr. LaFage’s family and friends struggled to understand this seemingly senseless act. I had no special access into the mind of the killer who was, I suspect, much like many of the hopeless, poor, angry inner-city youths of our country. But my teacher had given his students a means of making sense of behavior. He had offered us ways of seeing into the lives and conditions of other beings, so that we might begin to understand their aggression. We had learned that violence is the baseline strategy for most encounters between, and indeed within, species. This tendency is reduced only when there is a more successful adaptation to defending oneself or acquiring vital resources.

For most humans, the essentials of life — food, shelter, clothing, self-worth — can be had through nonviolent means. I have no doubt that this gentle and generous man would have given whatever material resource his assailant demanded. But what that angry, scared youth needed could not be given at the point of a gun, in a fleeting moment, on a New Orleans sidewalk. For the essentials of human life are not limited to bodily needs. And robbery is not always about material gain. Human cultural evolution has produced complex rules to constrain instinctual violence, but these norms must be learned within a viable social network. Even so, the development of human technology has outpaced behavioral adaptations. Our weapons enable us to draw and fire a gun much faster than another human can submit to our rage or plead for mercy.

So it was that Dr. LaFage’s teachings proved both vitally important and ultimately inadequate to understanding the genesis of human violence. I cannot weigh the despair of an inner-city teen; I have no formula that predicts when a fellow creature’s fear turns to rage. Nor can I graph a student’s affection for a gentle, demanding mentor. In the end, of course, Dr. LaFage was right: we cannot truly know the pain of others. Perhaps it is good that we cannot fully share in the anguish of terrified animals, dying men, grieving widows, fatherless children, or soulless youths. Sometimes our own sadness is as much as we can bear.