20
AT THIS POINT the ancient colony seemed doomed. Grow or die was the iron law it must obey. Population growth, positive or negative, up or down, is of life-and-death importance to any ant colony. Constant population growth and ever-rising productivity in the nurseries are the superorganism's bottom line. Both social and personal life are geared to serve this central purpose. The reason is elementary: the larger the colony, the greater its net growth, and hence the more virgin queens and males it can contribute to the next generation of colonies. Genes that prescribe robust colony growth spread across the land and through the species as a whole; those that do not prescribe robust growth shrink before the expanding Darwinian winners, and disappear.
The Trailheader myrmidons themselves instinctively knew they were in trouble. In time the chemical signals had dropped to a hardly detectable level in the outermost reaches of the nest. The workers began to understand that their Queen was incompetent.
Still, the instinct machine could not be turned off. The pheromone messages continued. They flowed ant to ant, spreading the latest news, the gossip, the health and wealth of the commonweal. The worker castes performed as before, and foragers still left in the early morning to search for food in the surrounding terrain. But the Trailheader workers had begun to change in subtle ways. The throttle of the colony was easing, a little at a time.
The Queen's health had been declining weeks before her death. The clues were all around her. Her egg production had plummeted, then halted. There were fewer and fewer larvae to feed. More nurse workers were idled, and colony growth slowed. The number of foragers taking the field dropped.
Yet there was hope for the colony. Even when the Queen still lived, the thinning of her pheromones had caused subtle changes in the bodies of young soldiers headquartered in the nest. These largest members of the worker caste had massive heads filled with powerful muscles, which slammed their sharp-toothed jaws together like serrated wire cutters. They were the iron, the physical power, the instinctual viciousness of the colony. They usually served only to defend the nest from intruders. Sometimes they went out along the odor trails with the ordinary workers to guard large food sources against rival colonies. But they also had the ability to reproduce. Their capacious abdomens contained a half dozen ovaries that, when enlarged by further growth, could produce viable eggs. Amazons all, they could change from warriors to mothers.
As the Queen pheromone declined, the soldiers were alerted. The sensory cells in the outer segments of their antennae noted the change. The information was relayed along nerve cells to the soldiers' brains. Circuits within the brains transmitted instructions to endocrine glands located elsewhere in the head. The hormones released from these glands stimulated growth in the ovaries of the young soldiers. Lines of eggs then appeared inside the ovaries. They began as microscopically small masses near the outer tips of the ovaries. The eggs grew in size as they migrated downward toward the openings of the ovaries, reaching maximum size just before they were laid.
The soldiers with the potential to become the new queens of the Trailhead Colony and no longer inhibited by the mother Queen pheromone abandoned their regular duties. With their ovaries swelling with eggs, they moved deeper into the nest interior and closer to the dwindling piles of larvae and pupae. As the last shards of the old Queen's body were carried into the cemetery, several of her rival successors began to lay eggs. They were now soldier-queens, and the only hope the colony had to restart its own growth.
The ordinary workers around them accepted the new status of the soldier-queens. Their tolerance represented a profound shift in the behavior of the colony as a whole. If the mother Queen had remained alive and well, and she had continued to broadcast her special scent, the response to any usurper would have been swift and violent. The Trailhead Colony had previously obeyed a basic rule of antdom: to reproduce in the presence of a healthy queen is strictly forbidden. The odds against success of such an affront to authority are long. The gamble is dangerous, and only a very few make the attempt. When a usurper starts to lay her own eggs and place them among those of a healthy queen, or even when she just becomes capable of doing so, she is harassed by her nestmates. Her sisters refuse to regurgitate food to her. They climb and stand over her, pulling at her legs and antennae. They may use their stings to cripple or kill her, or else spray her with a poisonous secretion. And they eat any eggs she manages to lay. Only when the Queen dies is the taboo lifted--and then only for a few individuals.
When the taboo ended in the Trailheader nest, a second crisis arose. The candidate royals began to quarrel among themselves for control. They converged on the brood chambers and jostled for position there. They struggled to climb on top of their rivals. Winners in these encounters seized their opponents' legs and antennae and dragged them away from the brood chambers. Unlike the thousands of their ordinary nestmates, they recognized one another as individuals. In time a dominance hierarchy formed, similar to pecking orders among chickens and rank orders among wolves. The Trailheader female who emerged as the alpha contender, in other words was able to chase away all her rivals, won the reproductive role. Egg-laying and larval growth resumed in a reduced but orderly manner. The crisis had ended by combat.
If the Trailhead Colony could not understand the history of its own species, how much did it know of its current condition? How could it make the right decision for survival? In fact, the Trailhead Colony knew a great deal. Worker ants are far more than just automated specks running around on the ground. Even with a brain only a millionth as big as that of a human, an ant can learn a simple maze half as fast as a laboratory rat, and remember the directions to as many as five different destinations when she forages away from the nest. After exploring a new terrain, a worker can integrate all the seemingly haphazard twists and loops she made and, amazingly, return to the nest in a straight line. She can learn and recall the special odor of the colony to which she belongs. In some species, she can recognize her own personal smell in odor trails over the ground to which she has contributed her own pheromones.
The Trailhead Colony, when all the learning and thought of its workers came together, was very smart by insect standards. With the unifying power of its Queen taken away and its population growth plummeting, it needed to act with all its group intelligence to regain its balance.
When one of the soldier-queens dominated its rivals and became the new Queen, the recovery of the colony seemed to get under way. A stream of eggs were laid. Larvae began to fill the empty brood chambers. Their odor and hunger signals joined with the pheromones of the new Soldier-Queen and spread through the nest. The power was returning. The workers found new energies. More foragers took the field.
One of the ants that led the way in restoring order was an elite worker that had served in the Queen's entourage during the final days. About ten percent of the worker force deserved this status, which they kept all their lives. All achieved it by labor; none belonged to the soldier caste, which was specialized for combat and called into action only when the colony was threatened. The elites were nervous and vigorous in movement. They initiated more tasks. They worked harder and more persistently, and they usually stayed on the job until it was finished. Other colony members were stirred to join them at the tasks they began. They were not just statistically at the upper end of the activity curve. They were a distinct group all on their own, forming a bump on the high end of the curve, and important to even a temporary prolonging of the life of the colony.
This particular elite worker was typical of her class in initiative and energy. After leaving the dead Queen, she proceeded directly to the nest entrance in search of new duties. Food was low, and fewer ordinary workers, grown lethargic, were leaving in search of new supplies. The defense of the colony had been weakened by the thinning of the sentinel force spread around the nest perimeter. Sensing the negligence of its nestmates, the elite left on solitary patrols, circling first close to the nest, then farther and farther away.
The renewed activity, led by the elites, was short-lived, however. The colony was destined to die, doomed by a hereditary trait even more basic than the altruism of the workers and the pheromonal ties that bound them together. The trait is the following. The Trailheaders, along with all ants of all kinds that ever existed back to the birth of ants in the late Jurassic period, used a strange but elegant genetic method to fix the sex of an individual at birth. Fertilized eggs develop into females, which can become queens or workers, and unfertilized eggs develop into males, which can do nothing but inseminate females.
The Soldier-Queen had never mated. Her children all arose from unfertilized eggs and were therefore male drones, contributing nothing to the welfare of the colony. They had weak mandibles and small brains but huge eyes and genitalia. They were wondrously adapted for mating after flying, up in the air with virgin queens, but even if that occurred it would do nothing for the Trailhead Colony. Those created by the Soldier-Queen would not mate with her or other potential Soldier-Queens. They were programmed to mate during nuptial flights away from the nest.
No way out existed for the Trailheaders; the colony was in a terrible fix. The linchpin of its social existence was gone and could not be replaced. Like a player in a Greek tragedy, it had been undone by the unfolding of events prescribed by its own unalterable nature. The source of its early success had become its fatal flaw. The colony could for a while contribute, through its production of males, to the gene pool of the population of colonies all around Dead Owl Cove, and in that way tweak out one more bit of Darwinian profit. But it could do nothing more for its own physical existence. With each passing day it became more vulnerable as a superorganism.
As the Trailhead Colony struggled in this pitiless world, its territory and even its very flesh were coveted by others. It would not merely fade away, holding on until a final worker sat alone in the nest. On the contrary, the neighboring colonies were likely to learn of its decline, and when that happened there would be war. And when war came, there was only the slimmest chance that the queenless Trailhead Colony could win.