Adventures Among Ants - Mark W. Moffett [42]
Unfortunately, despite my repeated, frustrating attempts to observe a colony’s establishment, the queens I managed to follow didn’t survive to rear workers. Nor did I find a marauder “starter” nest, or any nest with fewer than tens of thousands of workers—again, despite many long searches. So this part of my fieldwork remains tantalizingly incomplete. I’m eager to find out how a juvenile colony, lacking multitudes of ants, gets its food. While mass foraging becomes obviously advantageous when there’s a labor force that vastly outnumbers its quarry, perhaps droves aren’t necessary for success beyond that achieved by an ant foraging alone. If ants use a buddy system, even two workers, or at least a small group, might travel together to gang up on prey. Whether the developing marauder ant colony employs such a strategy is at present pure conjecture.
My failure to locate small nests suggests that extremely few new marauder ant colonies survive. Indeed, I often saw young queens, after their mating flight, being killed by workers from an established marauder nest. A queen’s survival likely requires her family to grow swiftly until it has a safely large population—a rare event. Fortunately, we can gain clues as to how colonies mature quickly from the marauder’s relative silenus. At Gombak Research Station, I excavated silenus nests, put the nest soil and all the stray workers in a bag, froze the bag, shook it up, counted all the ants in a tenth of the soil to estimate colony size, and then looked through the remainder of the bag for any queens. My colonies each contained one queen and from 64,000 to 127,000 workers. But I also found a nest of a few thousand workers and twenty-three wingless queens that clustered together amicably. The founding of a nest by a gathering of queens is called pleometrosis. With multiple queens laying eggs, the worker population no doubt increases rapidly, perhaps giving the colony a head start in foraging as a group.19
The diversus queens that I kept together likewise showed no aggression toward each other, though why each foundress attaches her eggs to her own body remains unclear. All the marauder colonies I dug up contained only one queen; if pleometrosis is common in this species, and in silenus, too, the number of queens must decline with time.
In contrast to marauder ants, army ant workers cull their queens before they mate. Typically, they raise several new queens, and when half their number depart with the chosen one to form a new colony, and the old queen goes her own way with the other half, the excess queens, blockaded by the workers, are left behind to die.
It seems the marauder ant workers likewise do the deed of disposing of excess queens, but in their case this occurs much later in the life of the colony. I learned this at the Botanic Gardens as I tallied workers who were repairing a damaged thoroughfare. At one point I noticed a group dragging a dusky object out of the nest and along their trail. Extracting it from them, I found in my hand a wingless queen with the worn mandibles and the near-black pigmentation of an aged animal. She was very much alive but had apparently outlived her usefulness to the colony and was being evicted. Twice more I saw the same event at nests sizable enough to suggest that marauder ant societies can retain more than one queen for a long time. Allowing these workers to finish their job, I watched them abandon the struggling queen at the side of their trail or in the garbage heap.
Calling the female reproductive ant a queen is a poor metaphor because ant royalty does not lead, and unlike human monarchs, they sire their minions. Nevertheless, the two varieties of queens share