The cast in this bug-world drama features four main players: the aforementioned Azteca instabilis ant, a tiny insect called the green coffee scale, the predatory lady beetle, and the parasitic phorid fly.
Tree-nesting Azteca ants enjoy a mutualistic relationship with the green coffee scale, which is a coffee pest. The ants protect the scale insects from predators and parasites and in return collect honeydew, a sweet, sticky liquid secreted by the green coffee scale.
The lady beetle eats the scale insects tended by the ants. However, patrolling ants attack and kill adult beetles and remove all beetle eggs laid bare on ant-tended coffee plants.
To get their offspring into food-rich patches among the scale insects, female lady beetles hide their eggs in out-of-the-way placesincluding the underside of the flat-bodied scale insects. That way, when the beetle eggs hatch they can start eating scale insects immediately, while still being protected from ant predation. A short time later, lady beetle larvae develop a waxy, filamentous coat that offers further protection from ants.
Phorids are a family of small, hump-backed flies resembling fruit flies. The parasitic phorid flies that attack Azteca ants lay their eggs on the ant's body. Fly larvae develop inside the ant's head, which falls off when the adult fly emerges. Phorids need to see movement to detect individual ants; therefore moving ants, rather than stationary ones, are their targets.
Needless to say, the ants do their best to avoid becoming phorid-fly victims. When the flies attack, the ants release a phorid-alert pheromone to warn other workers in the vicinity. In response, nearby ants enter a motionless, catatonic state and overall colony activity declines by at least 50 percent. This effect can last up to 2 ho
|Contact: Jim Erickson|
University of Michigan