Abstract:
Ectatomma ruidum is an abundant soil-nesting
Neotropical ant, which displays extensive behavioral
flexibility during foraging activities. We studied here one
unusual element of their behavioral repertoire: ambush
predation. A worker of E. ruidum waits near a nest of a
social sweat bee, Lasioglossum umbripenne, lunging at
incoming bees, or less frequently, at departing bees.
However, bees detected ambushing ants and modified
their behavior. Dead ants placed at bees’ nest entrances
significantly decreased bee activity, indicating that bees
recognized dead ants as potential predators. Neither simple
black models (square and rectangle) nor olfactory
cues had any effect on overall bee activity. A returning
bee usually approached her entrance and immediately
entered, but if an ant was waiting at the nest, a bee was
significantly more likely to abort the first approach flight
and then to re-approach the nest on the side opposite the
ant’s position. As models became increasingly ant-like,
returning bees more frequently aborted their first approach
flight, expressing other behaviors before entering
nests. These behaviors included withdrawal followed by
an approach from a different direction; zigzagging
flights, either from a distance or close to the entrance or
even a close inspection; landing a short distance from the
nest, then approaching on foot or waiting for several seconds
before entering. Ants responded with effective
counter-behaviors. Behavioral flexibility in nest entering/exiting
by L. umbripenne and in hunting strategy by
E. ruidum shows the complexity of this predator-prey relationship,
and illustrates the importance of information
processing by both species involved in determining the
outcome of the interspecific interaction.
