congresos y reuniones científicas
Activity patterns and parasitism rates of fire ant decapitating flies in their native Argentina
University of Charleston, Charleston, South Carolina, USA
Conferencia; 2008 Imported Fire Ant and Invasive Ant Conference; 2008
Institución organizadora:
University of Charleston
Daily and seasonal rhythms are intrinsic to virtually all life forms. In insects, as in many other organisms, the most evident rhythms are related with behaviors such as locomotion, flight, foraging, and oviposition. These behaviors are usually restricted to certain times of the day, because they are often synchronized with periodic events in the environment such as light and temperature cycles, or more episodic events related to food availability, predation, and competition. Little is known about phenological patterns in many insect groups, such as scuttle flies. Scuttle flies are one of the most biologically diverse groups of insects. Many of them are parasitoids or specific predators of other insects. The few studies of temporal rhythms in these flies were conducted almost exclusively on the fire ant decapitating flies because of the flies’ potential as biological control agents of the red and black imported fire ants in the United States. This work describes the diurnal activity patterns of two parasitoid fly assemblages of the red fire ant S. invicta in their native range in Argentina. Pseudacteon flies were censused monthly for one year at two sites in northwestern Corrientes province. Additionally, parasitism rates of S. invicta colonies naturally attacked in the field by Pseudacteon flies are reported for the first time from its native land. A total of 4,528 flies (86.3% females) of eight Pseudacteon species were collected attacking ants in the field. Pseudacteon litoralis Borgmeier and P. nocens Borgmeier represented 71-79% of female flies censused in both sites. Most species were active throughout the year, though abundances were variable over time and between sites. The highest occurrence peaks of flies were recorded in spring, while the lowest were in summer. Fly abundance was higher close to dusk, whereas species diversity was highest at midday. Cluster analysis separated similar two groups of species in each site. The first group corresponded to “crepuscular species” (P. nocens and P. litoralis), whereas the second one was composed by another five “midday species”. Only rhythms of activity of midday species were explained by climatic variables. Relationships among fly species were additionally established based on genetic nearness. For the most part, proximity phylogenetic and activity patterns seem not be related. Only P. litoralis and P. nocens 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.