Release and Establishment of the Little Decapitating Fly Pseudacteon cultellatus (Diptera: Phoridae) on Imported Fire Ants (Hymenoptera: Formicidae) in Florida Author(s): Sanford D. Porter, Vivek Kumar, Luis A. Calcaterra, Juan A. Briano and Dakshina R. Seal Source: Florida Entomologist, 96(4):1567-1573. 2013. Published By: Florida Entomological Society DOI: http://dx.doi.org/10.1653/024.096.0440 URL: http://www.bioone.org/doi/full/10.1653/024.096.0440 BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/ terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Porter et al.: A New Fire Ant Decapitating Fly in Florida 1567 RELEASE AND ESTABLISHMENT OF THE LITTLE DECAPITATING FLY PSEUDACTEON CULTELLATUS (DIPTERA: PHORIDAE) ON IMPORTED FIRE ANTS (HYMENOPTERA: FORMICIDAE) IN FLORIDA SANFORD D. PORTER1,*, VIVEK KUMAR2,4, LUIS A. CALCATERRA3, JUAN A. BRIANO3 AND DAKSHINA R. SEAL2 1Center for Medical, Agricultural and Veterinary Entomology, USDA-ARS, 1600 SW 23rd Drive, Gainesville, FL 32608, USA 2Tropical Research and Education Center, University of Florida, 18905 SW 280th St, Homestead, FL 33031, USA 3Fundación para el Estudio de Especies Invasivas, Bolívar 1559 (B1686EFA) Hurlingham, Buenos Aires, Argentina 4Current Address: Mid-Florida Research & Education Center, University of Florida, 2725, S. Binion Road, Apopka, FL 32703, USA *Corresponding Author; E-mail: [email protected] Supplementary material for this article in Florida Entomologist 96(4) (2013) is online at http://purl.fcla.edu/fcla/entomologist/browse ABSTRACT The little decapitating fly Pseudacteon cultellatus Borgmeier (Diptera: Phoridae) from Ar- gentina was released as a self-sustaining biological control agent against the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae) in Florida to parasitize small fire ant workers associated with multiple-queen colonies. This fly appears to be established at 2 of 5 release sites, but populations still remain very low () 1% of total Pseudacteon flies) and localized more than 2 yr after their release. Further releases of P. cultellatus in the United States should be limited to a few additional sites in different habitats or climatic regions where this fly might be more successful. Key Words: Solenopsis invicta, biological control, field release RESUMEN La mosca pequeña decapitadora Pseudacteon cultellatus Borgmeier (Diptera: Phoridae) de Argentina fue liberada como un agente de control biológico autosustentable contra la hor- miga de fuego importada, Solenopsis invicta Buren (Hymenoptera: Formicidae), en Florida para parasitar obreras pequeñas de esta hormiga asociadas a colonias con múltiples reinas. Esta mosca parece estar establecida en dos de los cinco sitios de liberación, pero la pobla- ción sigue siendo muy baja () 1% del total de las moscas liberadas) y focalizada más de dos años después de su liberación. Nuevas liberaciones de P. cultellatus en los Estados Unidos deberían estar limitadas a unos pocos sitios adicionales en diferentes hábitats o regiones climáticas donde esta mosca podría ser más exitosa. Palabras Clave: Solenopsis invicta, control biológico, liberaciones de campo Imported fire ants (Solenopsis spp.; Hymenop- selected for release as a self-sustaining biological tera: Formicidae) in North America have popula- control agent for imported Solenopsis fire ants in tion densities 5-10 times higher than those nor- the United States because this species parasit- mally found in their South American homelands izes the smallest sizes of fire ant workers. Small (Porter et al. 1992, 1997). Escape from numerous fire ant workers are the most abundant size class natural enemies left behind in South America is in fire ant colonies, especially in young colonies a likely reason for intercontinental differences in (Porter & Tschinkel 1985a, 1985b) and in mul- fire ant abundance (Porter et al. 1997). tiple-queen or “polygyne” colonies (Greenberg et The little decapitating fly (Pseudacteon cultel- al. 1985). Polygyne fire ant colonies are found in latus Borgmeier; Diptera: Phoridae; Fig. 1) was about 10-15% of the imported fire ant range in the 1568 Florida Entomologist 96(4) December 2013 Fig. 1. Male and female Pseudacteon cultellatus decapitating flies (left). A posterior view of the ovipositor (right) by which female flies are easily identified (Porter & Pesquero 2001). The male can be distinguished in the United States by its small size, triangular anal tube, and a dark-brown hairy antenna with a narrow curved apical exten- sion. The gray scale line is 0.5 mm (left) and 0.2 mm (right). United States, except in Texas where 50% of the al. 2008; Porter & Calcaterra 2013), and Pseudac- state has multiple-queen fire ants (Porter et al. teon nocens Borgmeier (Plowes et al. 2012). 1991; Porter 1992; Porter et al. 1992). The objective of this paper is to document the Like other Pseudacteon flies, when P. cultella- release of P. cultellatus, a sixth species of fire ant tus maggots are ready to pupate, they decapitate decapitating fly, at 5 sites in Florida and the es- their host workers and use the newly emptied tablishment of this fly at 2 of these sites. host head capsules as pupal cases (Porter 1998). All Pseudacteon species that attack fire ants, MATERIALS AND METHODS including P. cultellatus, appear to be specific to Solenopsis fire ants (Porter & Gilbert 2004; SDP The original P. cultellatus flies used in this unpublished data). study were collected in Dec 2006 from a marsh The natural geographic range of P. cultella- area along the Parana River (~2,700 flies) about tus in South America is from Buenos Aires, Ar- 20 km NE of Corrientes, Argentina (S 27.371° W gentina, north through Corrientes, Argentina, 58.687°) and from a picnic/camping area (~2,000 then northeast into Brazil through the states flies) about 20 km SE of Corrientes (S 27.559° W of Parana and São Paulo to the states of Minas 58.725°). Most of the host ants at these sites were Gerais and Goias (Patrock et al. 2009). In South S. invicta, but local biotypes of S. invicta were America, this species is known to attack both red probably not as similar to US biotypes as those and black fire ants (i.e.; Solenopsis invicta Buren found further north along the Paraguay River in and Solenopsis richteri Forel) and probably So- the province of Formosa (Ascunce et al. 2011). Im- lenopsis saevissima F. Smith as well. The most mature stages of P. cultellatus were carried to a abundant populations were found in gaps in sub- USDA quarantine facility in Gainesville, Florida tropical gallery forest habitats (Calcaterra et al. in parasitized hosts accompanied by an Argen- 2005). The climatic preferences of P. cultellatus tine export permit (DFS N°19517) and a USDA/ flies are rather broad ranging from tropical to APHIS import permit (#64943). temperate; consequently, its potential range in Prior to field release in 2010, the flies were the United States could be anywhere imported mass reared on red imported fire ants from the fire ants are found. United States using large attack boxes (1 m wide Five species of phorid decapitating flies have × 2-2.5 m long × 0.7 m high) with either 8 or 14 been released and established as fire ant biocon- smaller attack trays similar to those described trol agents in the United States: Pseudacteon by Vogt et al. (2003) except that humidity was tricuspis Borgmeier (Callcott et al. 2011), Pseu- controlled by a vaporizer in a chamber mounted dacteon curvatus Borgmeier (Callcott et al. 2011), under the attack chamber. Every morning, new Pseudacteon litoralis Borgmeier (Porter et al. flies emerged from pupation trays directly into 2011), Pseudacteon obtusus Borgmeier, (Gilbert et the attack chamber where they could parasitize emergence ofthe flieslongerthanwasdesirable. peratures (15-20 °C)intheearlyspringdelayed Also, coolgroundtem- the coolerbox anditslid. release fliesweretrappedin thecrackbetween ments becauseaboutonequarter ofthe13,600 implementation ofthismethod neededimprove- the methoddescribedbyPlowes etal.(2012).Our solated boxwithanexitpipe inthetopsimilarto was donebyburying 1) release(Table etal.2006).The2011 Vazquez curvatus P. in parasitizedantsaswaspreviouslydonewith 1)usedlarvae 4 releasesconductedin2010(Table The drought orhotweather(Plowesetal.2011). ensure refugiaforthefireantsandfliesincaseof as possibletobushes,trees,andwatersources releases wereconductedusingmoundsasclose The siteswereallinopendisturbedareas,but like thoseassociatedwithpolygynecolonies. m2; Macom&Porter1996)withsmallworkers lations offireants(probably1500-3000workers/ Sites wereselectedwhichcontainedlargepopu- 1). Florida beginninginthespringof2010(Table tary Materialabove). were activeintheholdingbox(seeSupplemen- darkened nestsfortheworkerssofewer