Colony-level impacts of parasitoid flies on fire ants

*[In the laboratory, we show that an average phorid density of as little as one attacking fly per 200 foraging ants decreased colony protein consumption nearly 2-fold & significantly reduced numbers of large-sized workers 50 days later. The high impact of a single phorid occurred mainly because ants decreased foraging rates in the presence of the flies. Our experiments, the first to link indirect & direct effects of phorids on fire ants, demonstrate that colonies can be stressed with surprisingly low parasitoid densities.]