Adventures Among Ants - Mark W. Moffett [126]
Is there a downside to the garden fungus’s life of privilege? The ants’ constant pruning and eating of the fungus prevents the garden from forming mushrooms. The ants thereby obstruct the reproduction of their cultivar, which, like the many kinds of fruit and vegetables similarly pruned by humans, spreads only asexually within the gardens. This lack of sexual reproduction may help assure the continued compatibility of the cultivar with its host, by keeping the desirable traits of the cultivar intact.8 Only after the death of the colony can the gardens seize the moment before they starve from a lack of mulch to sprout gilled mushrooms and interbreed.9
The mode of transmitting their gardening methods couldn’t differ more between ant and human. Issues of lactose intolerance or allergies to wheat aside, most of the changes humans have undergone in their transformation to agriculturalists have been learned rather than genetic.10 Though such social learning is known in ants, no worker has the brainpower or longevity for a complex education. Thus leafcutters have encoded gardening in their genes, with the exception of a few variables such as a forager’s preference for the plants she knows best. In gaining the ability to farm, leafcutters have lost the ability to survive any other way. But agriculture provides the ants with a dependable supply of nutrition, buffering them from whatever disasters—floods, desiccation, disease—might befall the world outside the nest. When little vegetation is available to harvest, for example, the gardens shrink gradually but continue to provide food for weeks.
There are examples of farming and domestication among other ants as well: in a similar, two-way accommodation, certain ants have in a sense domesticated the plants that provide them room and board. Ant species that tend herbivores such as aphids and their sapsucking relatives come close to practicing a form of husbandry. That these “cattle” have been domesticated is shown by their adaptations to life with ants, whereby some of the husbanded insects forgo their ancestral defenses, such as chemical sprays or leaping, in favor of a dependency on ant protection services.11 In humans, the pastoral way of life succeeded agriculture, about 6,000 years ago, with the domestication of goats, cattle, and sheep, whereas ant “dairy” farming probably preceded their cultivation of fungus, likely going back 100 million years or more.12 Fungus gardening is a complex task for ants compared to the simplicity of tending honeydew-producing insects, which don’t need to be fed or penned and aren’t dependent on the ants for their survival.
Herdsmen ants guarding their aphid “cattle” in Pasoh, Malaysia. The workers carry the aphids everywhere and protect them at night within bivouac nests.
In some mutualisms, however, ants and their herbivore “cattle” are completely codependent. The domesticated mealybugs of Asian herdsmen ants are never found without their ants, which carry them to fresh pasture—young foliage—in incessant migrations that recall the life of nomadic peoples. Like a leafcutter queen who brings a starter fungus with her to found a nest, a herdsman queen takes a mealybug on her nuptial flight to establish her own herd. In addition to drinking the honeydew, certain ant species cull their herds for meat. This makes such herders, much like the leafcutters with their fungus and leaf sap diets, virtually self-sustaining.13
HYGIENE
The sun was up and the flaming orange-red Pogonomyrmex maricopa harvester ants were running along well-trodden trunk trails to collect seeds, when a worker walked a couple of feet from the disk of white sand that marked her nest entrance and stood stiffly, high on her legs, with head and abdomen raised and jaws agape. Near her was