Individual and colony level variation of phorid fly parasitoid host preference in the ant Azteca sercieasur in coffee agroecosystems

Background/Question/Methods

The aggressive arboreal ant, Azteca sericeasur, ubiquitous over the New World Tropics, has been shown to act as an effective biological control agent in coffee agroecosystems.  However, a suite of three species of Pseudacteon genus phorid fly limit the ability of A. sericeasur to prey on coffee herbivores.  Phorid fly parasitoids utilize a multimodal cues to locate and successfully parasitize their hosts.  Here we examine whether this suite of phorid flies uses morphological, behavioral and/or chemical variation in individual ants to select a host.  Using filmed behavioral assays in the field and Observer software, we analyzed the behavior and ant size differences between ants on the individual and colony level as phorid flies arrived and attacked the ants.  Individual ants from these colonies were also collected and their cuticular hydrocarbons were extracted and analyzed in the lab using Gas Chromatography/Mass Spectrometry.

Results/Conclusions

Phorid flies show variation in host preference based on size and behavior of individual ants.  Phorid flies also show distinct preferences for ants within certain colonies and ants with certain cuticular hydrocarbon chemotypes.  These host preferences vary based on phorid fly species.   Phorid fly parasitism on Azteca sericeasur not only causes ant mortality, but also reduces the ant’s ability to forage by about half, thus reducing their effects as a biological control agent within coffee agroecosytems.  Understanding how this suite of phorid fly successfully parasitize their hosts may have important management implications in these dynamic agroecosystems.