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

LUIS A. CALCATERRA, ALICIA DELGADO, AND NEIL D. TSUTSUI

ANNALS OF THE ENTOMOLOGYCAL SOCIETY OF AMERICA

ENTOMOLOGICAL SOC AMER

Año: 2008 vol. 101 p. 539 - 550

0013-8746

This work describes the annual and daily activity patterns of two parasitoid ßy communities of the Þre ant Solenopsis invicta (Hymenoptera: Formicidae) in their native range in Argentina. Pseudacteon (Diptera: Phoridae) ßies were censused monthly for 1 yr at two sites in northwestern Corrientes province. Additionally, parasitism rates of S. invicta colonies naturally attacked in the Þeld by Pseudacteon ßies are reported for the Þrst time from its native habitat. In total, 4,528 ßies (86.3% females) of eight Pseudacteon species were collected attacking ants in the Þeld.Solenopsis invicta (Hymenoptera: Formicidae) in their native range in Argentina. Pseudacteon (Diptera: Phoridae) ßies were censused monthly for 1 yr at two sites in northwestern Corrientes province. Additionally, parasitism rates of S. invicta colonies naturally attacked in the Þeld by Pseudacteon ßies are reported for the Þrst time from its native habitat. In total, 4,528 ßies (86.3% females) of eight Pseudacteon species were collected attacking ants in the Þeld.Pseudacteon (Diptera: Phoridae) ßies were censused monthly for 1 yr at two sites in northwestern Corrientes province. Additionally, parasitism rates of S. invicta colonies naturally attacked in the Þeld by Pseudacteon ßies are reported for the Þrst time from its native habitat. In total, 4,528 ßies (86.3% females) of eight Pseudacteon species were collected attacking ants in the Þeld.S. invicta colonies naturally attacked in the Þeld by Pseudacteon ßies are reported for the Þrst time from its native habitat. In total, 4,528 ßies (86.3% females) of eight Pseudacteon species were collected attacking ants in the Þeld.Pseudacteon ßies are reported for the Þrst time from its native habitat. In total, 4,528 ßies (86.3% females) of eight Pseudacteon species were collected attacking ants in the Þeld.Pseudacteon species were collected attacking ants in the Þeld. Pseudacteon litoralis Borgmeier and Pseudacteon nocens Borgmeier represented 71Ð79% of female ßies censused in both sites. Most species were active throughout the year, although abundances were variable over time and between sites. The highest occurrence peaks of ßies were recorded in spring, whereas the lowest occurrence was in summer. Fly abundance was higher close to dusk, whereas species diversity was highest at midday. Relationships among species were established based on their activity patterns and genetic proximity. The presence and abundance of four species were explained by climatic variables, whereas two species may have inherited similar circadian rhythms from a common ancestor. Overall, the parasitism rate by the nine species recorded was very low (0.24%). The highest percentage of parasitized workers was found in spring (0.5%) and occurred within the most complex habitat (gallery forest). The highest parasitism rate per site and colony was also for this habitat in spring (1.16 and 2.81%, respectively). The highest rates of emergence were recorded for Pseudacteon nudicornis Borgmeier.Borgmeier and Pseudacteon nocens Borgmeier represented 71Ð79% of female ßies censused in both sites. Most species were active throughout the year, although abundances were variable over time and between sites. The highest occurrence peaks of ßies were recorded in spring, whereas the lowest occurrence was in summer. Fly abundance was higher close to dusk, whereas species diversity was highest at midday. Relationships among species were established based on their activity patterns and genetic proximity. The presence and abundance of four species were explained by climatic variables, whereas two species may have inherited similar circadian rhythms from a common ancestor. Overall, the parasitism rate by the nine species recorded was very low (0.24%). The highest percentage of parasitized workers was found in spring (0.5%) and occurred within the most complex habitat (gallery forest). The highest parasitism rate per site and colony was also for this habitat in spring (1.16 and 2.81%, respectively). The highest rates of emergence were recorded for Pseudacteon nudicornis Borgmeier.Pseudacteon nudicornis Borgmeier.Borgmeier.