PHENOLOGICAL PATTERNS FOR PARASITOIDS SPECIALIZED IN ATTACKING SOLENOPSIS FIRE ANTS, AT THE RESERVA ECOLOGICA COSTANERA SUR, ARGENTINA

¹Centro de Estudios e Investigaciones, Universidad Nacional de Quilmes, Roque Saenz PeŇa 180, 1876 Bernal, Bs As, Argentina, E-mail pfolgarait@unq.edu.ar
²Department of Zoology, University of Texas, Austin, TX 78712, USA.

We have been sampling every month phorid populations attacking Solenopsis richteri ants at the Reserva Ecologica Costanera Sur, Argentina, for the past four years. We estimated the abundance of phorids as the number of phorids collected per hour of sampling effort; data presented here show phorid abundance per month joining data for all the years. Phenological data showed strong seasonal patterns related to temperature and precipitation, and allowed the discrimination between season and trail/mound generalist versus specialist species and abundant versus rare species. The most abundant and constant species was the mound-specialist P. borgmeieri, being the single species present during the winter; its abundance was negatively correlated with temperatures and precipitation and was classified as a winter specialist. P. obtusus was a trail specialist and the most rare one, found only during the fall and spring; its abundance was positively correlated with temperature and precipitation. The other 4 species were present in 8 of the 12 months. The most abundant P. curvatus showed its peak during the summer when temperatures were greatest and precipitation intermediate, and was considered a hot specialist. The second most abundant was the fall specialist P. nudicornis which attained greatest abundance during the fall, and less during spring, when temperatures were intermediate but precipitation highest; we classified it as a fall specialist. P. comatus, the other mound-specialist, had intermediate to low but constant abundances that were correlated positively with temperature and precipitation. P. tricuspis with the least abundance seemed to be a summer species which activity was positively correlated to temperature but not to precipitation. Phorid abundance showed a negative relationship with wind speed at ground level. Phorids seemed to track ant activity throughout the year with a peak of activity for both groups during the summer. The abundance of mound-phorids resembled the total abundance of phorids, with a peak in March mainly due to the generalists P. curvatus and P. nudicornis. The abundance of trail-phorids peaked in January. From a biological control perspective, it will be profitable to consider for introduction more than one species, selecting those with greater abundance and complementary phenology and searching behavior. Selected species should have similarities in climatic conditions between sites of origin and of introduction of these phorid species.

Index terms: Argentina, climate, fire ants, phorids, phenology