Activity Patterns and Parasitism Rates of Fire Ant-Decapitating Flies (Diptera: Phoridae: <I>Pseudacteon</I> spp.) in Their Native Argentina

Biology of Pseudacteon Decapitating Flies (Diptera: Phoridae) That Parasitize Ants of the Solenopsis saevissima Complex (Hymenoptera: Formicidae) in South America

“…Furthermore, the abundance patterns of phorid flies usually vary among different areas. For instance, six species of S. invicta-decapitating flies were found active throughout the year in Corrientes [30], whereas only one species of S. richteri-decapitating fly was active throughout the year in Buenos Aires [50]. The warmer winter in Corrientes explains greater phorid activity throughout the year.…”

“…Only 11-35% of oviposition attempts result in successful parasitism and larval development in laboratory tests [6]. In native Argentina, the maximum parasitism rate per S. invicta colony by phorid flies is around 2.8% [30]. The low success rates may be attributed to the following possibilities: (1) oviposition strikes are too rapid to eject an egg, (2) flies are selective to quality of workers for egg laying through oviposition attempt, and (3) some of the oviposited eggs do not develop due to infertility or ant defenses [16].…”

“…Most phorid fly species are active throughout the year in their native range but with different seasonal and daily activity patterns. The abundance of flies in South America is generally high in spring, possibly due to significant host colony activity caused by the mating flights and/or because of the start of the rainy season [30,52]. The peak abundance varies with fly species throughout the year.…”

“…Overall abundance for a given species can be high in spring and fall in northeastern Argentina and in summer in east central Argentina [47]. In Argentina, at least six common fly species, P. cultellatus, P. litoralis, P. nocens, P. obtusitus, P. obtusus, and P. tricuspis, are abundant and present in each month [30,48]. As they oviposit all year round in a temperature range of 18-40 • C, these flies have continual overlapping generations [5].…”

The introduction of the fire ant parasitoid Pseudacteon nocens in North America: challenges when establishing small populations

“…Direct impacts through worker mortality are low with field rates of parasitism usually less than 1% (Calcaterra et al 2008;Morrison and Porter 2005) however indirect effects on colony health through reduced foraging efficiency and defenses (Feener and Brown 1992;Folgarait and Gilbert 1999) or even as pathogen vectors (Valles and Porter 2007) may provide important population level impacts, especially on environmentally stressed colonies.…”