Effects of phorid flies (Pseudacteon sp.) on the foraging and persistence of the ladybeetle (Azya orbigera) in an organic coffee system

Trait-mediated effects are known to be very important in shaping biological communities. Behavioral changes in any organism within a community might change the interactions or the strength of the interactions between the other members of the community. Such is the case of the behavioral changes that the parasitoid Pseudocanton sp. (Diptera: Phoridae) inflicts over its host Azteca instabilis (Hymenoptera: Formicidae) in a coffee plantation in Chiapas, Mexico. Previous studies have found that the activity of A. instabilis is greatly reduced in the presence of this parasitic fly. With this study we wanted to determine if this reduction of activity interrupts the protection against natural enemies that A. instabilis gives to its mutualistic partner, the green coffee scale (Coccus viridis, Hemiptera: Coccidae). To answer this question we compared the effects of phorid presence on 1) the predation rate of the ladybeetle Azya orbigera (Coleoptera: Coccinellidae) preying upon green scales tended by A. instabilis inside insect rearing cages, and 2) the time it takes A. instabilis to force A. orbigera off of a coffee bush infested with green scales. We found that the presence of phorid flies increased the time before A. orbigera was forced off of a coffee bush and significantly increased the amount of green scales eaten by this ladybeetle in 24 hours. These results show how trait-mediated effects caused by the presence of a parasite can disrupt a mutualistic association and allow a predator to gain access to otherwise non-accessible prey.