Distribution and bionomics of Orasema xanthopus (Hym: Eucharitidae), parasitoid of fire ants in Argentina

VARONE, LAURA; BRIANO, JUAN A.

Charleston

Congreso; Imported Fire Ant Conference; 2008

Entomological Society of America

The Eucharitidae are parasitic wasps of ants and have an unusual life cycle. The females lay the eggs in plant tissue near the ant nests; the emerged planidia attach themselves to a foraging worker ant and are carried to the nest phoretically. In 2005 studies started at SABCL on the evaluation of this wasp as biological control agent of Solenopsis invicta and S. richteri in the United States. Surveys were conducted in northern and central Argentina to establish wasp?s natural occurrence. Positive sites were revisited and the Corrientes Biological Station (CBS) was selected to conduct ecological studies because of the high prevalence and parasitism rate of O. xanthopus on fire ants. In the field, oviposition substrates and adult activity were evaluated. In the laboratory, oviposition substrates, female survivorship and fertility were assessed. A total of 458 Solenopsis spp. colonies were excavated at 56 sites, from which 24 resulted positive with O. xanthopus present in 30.8% (range 12.5-100%) of the colonies. In the field and the laboratory, O. xanthopus showed a broad range of substrates for oviposition. Survival was estimated in 3.6 ± 1.5 days (n=30) and fertility in 613 ± 114 eggs/female (n=10) upon emergence, suggesting that O. xanthopus is a pro-ovigenic species. Adult activity of O. xanthopus was concentrated at noon and the presence of adults outside the ant nest did not indicate the presence of a parasitized colony.