Adventures Among Ants - Mark W. Moffett [80]
A scorpion being carried into the canopy by weaver ants at Kirirom National Park, Cambodia.
One day during my stay in Cambodia, I was overturning rocks in the forest when out from under one scrambled a 5-centimeter-long scorpion. Though fierce enough that I couldn’t grasp it with my forceps, the scorpion was immediately seized and held in place by a single weaver ant—doubtless one-thousandth its weight—until backups arrived to pin its limbs. The expanded soft pads on weaver ant feet allow them to maintain their grip on their substrate, even when their bodies seem stretched to the breaking point.27 According to one report, a lone weaver ant was able to support the full weight of a 7-gram baby bird that hung below her.28
Two dozen workers ganged together to haul the scorpion 6 meters up a tree in about the same number of minutes. When I extracted the leviathan from their grip, he was groggy but alive. Weaver ants don’t gnaw off limbs to immobilize their quarry, as marauders do. Death is thought to come from being pulled with enough force to dislocate appendages, though few limbs break free. But I suspect the ant bites, with their acidic secretions that leave me feeling dizzy after a day in the field with these ants, deliver toxins as well.
Against powerful invertebrates like scorpions, short-range recruitment and drawing-andquartering techniques are very effective, and such prey could represent a larger part of the food intake of weaver ants than it does of army ants. Though small arthropods are the foundation of their diet, weaver ants may even target vertebrates: one colony in Cameroon contained the remains of two lizards, a snake, a bat, and three birds. Though we don’t know if the ants slew the animals or found their corpses, the workers can kill a bird by pulling it taut, their dozens of bodies linked in chains like those formed when they build nests. Perhaps to avoid theft from even larger animals, weaver ants conceal hefty prey under leaf litter while they subdue it and organize transport on the ground.29 When the carcass has reached its final canopy destination—as Conservation International biologist David Emmett told me happened in Phnom Penh with a 15-centimeter-long dogfaced fruit bat—workers often construct a leaf encasement around food, similar to the soil barricades made by marauder ants. This permits both species to eat in privacy—in the case of the dogfaced bat, down to and including many of the bones.
No adult ant can swallow the prey she kills because solids can’t pass through her impossibly narrow waist to reach her stomach. Instead ants drink the fluids oozing from its body, perhaps after some chewing. Many species use child labor—just as weavers do to build their nests—to transform prey into a form the workers and queen can ingest. Workers of Arizona’s Pheidole spadonia “big-headed” ants place chunks of prey in a bowl-like depression on the bellies of their larvae; the larvae spit out digestive enzymes that dissolve the meat into something like a protein shake for the adults, which slurp up what they want and feed the rest back to the larvae.30 The Adetomyrma “Dracula ant” of Madagascar takes a more gruesome approach. The workers immobilize prey such as centipedes with their virulent stings, then move their larvae to the food, which chew it up. After a larva has eaten, the workers pierce its thin skin to drink the hemolymph that leaks out, leaving their young literally scarred for life.31 Larvae of Asian Leptanilla avoid such blood-letting: they are fitted with spigots from which the adult ants can obtain a drink.32
Weaver ant workers have other sources of liquid sustenance. Not nearly as meat reliant as army ants, they are partial vegetarians, which has advantages, as they are always