Grasshopper Aggression

When does an inoffensive little green grasshopper transform into a ravenous beast that destroys crops? When it becomes a locust. Mention the word locust to many people and it conjures up an image of a horde of voracious insects that invade and eat everything green in sight. Like army ants or a swarm of mosquitoes, locusts congregate in vast clouds of plunderers which will quickly consume precious plants and then move on, leaving behind a barren landscape.

It's interesting that only recently have scientists figured out where locusts come from. They seem to pop out of nowhere, do their damage, and move on. What triggers their amassing and subsequent invasion? Recent studies have shown that locusts are the Hyde side of the gentle Dr. Jekyll—from Robert Louis Stevenson's tale The Strange Case of Dr. Jekyll and Mr. Hyde, in which Hyde becomes the evil alter-personality of the good doctor.

When hard times come—such as drought or famine—hungry grasshoppers begin to cluster and rub up against one another. This pushing, shoving, and agitation releases serotonin into their bloodstream and brains. Suddenly they begin to grow larger, they turn from green to black and yellow, they crowd even closer and become aggressive. Soon they're on the rampage, as the swarm moves off, looking for food. It's as if their stressful behavior spreads through the mob, turning them into a threatening horde. Their interactions can become so belligerent that they will later turn to cannibalism, as plants become increasingly scarce. Like a bad dream, locusts abruptly appear, do their frightening thing, and then disappear.

Entomologists have known the basic qualities of locusts, but have not given them the attention they deserve. Why might that be? One theory suggests that humans see themselves as similar to gentle grasshoppers—in that, under stress, we too change our personality. We'd prefer to view ourselves as having a fixed personality—in which we present an enduring face to others. We also like to believe that we're in charge of who we are and can control our behavior. Instead, our environment plays a significant role in how we behave; other people directly influence us and cause us to act in different ways. Sometimes we literally get out of control. We can do significant damage. Tension can turn us into abusive beings.

So are we humans sometimes like the gentle grasshopper, munching imperturbably on our thoughts, in command of our behavior, staying cool when disturbed? Or are we reactive critters who, under stress, turn nasty and beat up on others? Are we grasshoppers or locusts? Or both?

Brain-like Ant Colony

An ant colony, according to some neuroscientists, operates roughly analogous to the human brain, where each ant behaves something analogous to a neuron. Individual ants communicate by chemical signals, which determines the overall behavior of the colony. Similarly, our neurons communicate via electrical and chemical signals, which result in our behavior.

If this analogy is appropriate, it raises the question, do ant colonies remember? Human memory is the result of many neurons acting together—creating retrievable recollections of past events and experiences. Our recall depends on how individual neurons stimulate each other. Short- and long-term memories employ different collections of neurons. Every time we summon up a memory, we rearrange some of the neural circuits and then send the memory back into “storage,” slightly altered. In this way, memories will gradually morph over time—although we tend to believe there's a constancy and an accuracy to our recollections. That certainty is really not there, however.

Furthermore, our memories are not just housed in some unique place deep in our brain. Our bodies—riddled with nerves and neurons—also remember. There's so-called “muscle memory,” by which we retain the knowledge of how to ride a bike or play a musical instrument. In response to wounds and germ attacks, antibodies and molecular receptors are created; they “remember” these events. The same mechanism happens for plants—trees “remember” physical wounds and insect attacks, so as to both heal and better respond in the future.

Back to ant colonies: If each ant is somehow comparable to individual brain neurons, and signals between ants are somehow comparable to neuronal communication, does the congregation of ants—the colony—display memory? Indeed it does. Although there is no central control agent in an ant colony, the community can remember, and that memory persists over days, months, and even years. Although an individual ant has a life span of months, the colony can live for up to 30 years, the lifetime of the queen. I have written before of the phenomenal behavior of an ant colony, as it performs activities far beyond what a single ant can do—such as tend graveyards and gardens, keep the nest clean, coordinate attacks, etc. These abilities depend to some extent on memory.

In fact, researchers have discovered that while individual ants can only briefly remember the location of food, the colony retains that knowledge for much longer periods of time. What's more, an older ant colony acts more wisely than a younger colony—showing an accumulation of knowledge over time.

The enhanced performance of large collections of individual creatures is often described as an emergent property. It is a process that has yet to be fully understood. Similarly, our memory—and in fact, our consciousness—still have much to be explained.

So if an individual ant can be considered to be something analogous to a brain's neuron, we might be grateful that an ant colony contains only thousands of ants. Were those colonies to be inhabited by a few million—or, God forbid!—a few billion insects, they would be smarter than us! Doesn't the possibility of having the Earth ruled by ant colonies seem frightening?

Spring Wildflowers

Spring brings it blossoms. Dandelions are mostly regarded as a weed, but its blossoms are beautiful. Click to enlarge.

Secret of the Stripes

Why have zebras evolved those brilliant, even showy stripes? It's as if they are blatantly advertising their presence, which makes no sense on the African savanna, where many lions look to make a meal of them. Their stripes cannot be interpreted as camouflage, since they stand out so strikingly. So what's going on? There's nothing subtle about their alternating bands of black and white. They stand out as if their coloring announced their presence with a trumpet blare.

Researchers have posited a few explanations of why evolution gave the zebra such a gaudy decoration. What are some of their postulates for zebra stripes? One prominent idea is that, although the stripes are conspicuous, they are illusory. All those random stripes in a herd of zebras can confuse a predator—it makes it difficult for predators to figure out an individual zebra's size, speed, or trajectory. Secondly, the zebra stripes may serve a social function for other zebras—either as part of the process of sexual selection, or a means to identify each individual zebra. Then a third possibility is for thermal regulation: the black stripes soak up more of the sun's energy, thus causing warm air to rise over them, which pulls in air from the adjacent white stripes, creating an airflow over the zebra's body, to cool it a bit, on a hot African afternoon.

Then there's a fourth hypothesis: those stripes could be an evolved defense against biting flies. Zebras, unlike horses, evolved in parts of the world inhabited by nasty, biting flies that carry diseases. That possibility gained credence recently, when researchers compared solid-colored horses to zebras—as to which equine was more susceptible to bites. What they found was that solid-brown horses had flies land on them much more often than on nearby zebras. One could ask, however, if horses and zebras might have a different smell—maybe horse odors are more to the liking of biting flies? The researchers had that possibility covered, when they threw zebra-striped blankets over the horses and noted that flies continued to land on their heads, but not on the stripes.

So the difference must be visual—something like what happens with lions. As the researchers watched, they noted that when the flies zeroed in on a zebra, they did not slow down and land, as they did for the horses. The guess is that flies' low-resolution vision caused them to view horses and zebras the same from a distance, but when a fly got close it suddenly saw stripes and got confused, and veered off without landing.

Now here's the part that caught my eye: the researchers suggest that when we humans venture outdoors where biting flies may be looking for us, wear patterned clothes, or try applying striped body paint. I have written before on this blog about being pestered by large horseflies that can inflict a painful bite. My most vulnerable time is when I'm naked, headed to or from my outdoor tub. Maybe I should get a zebra-striped robe to wear? Or a more permanent solution: get tattooed with black and white stripes? I could join the circus and be featured in the freak show, or maybe go on safari, and not worry about being attacked by a lion (or biting fly).