SYSTEMATICS Pseudacteon calderensis, a New Fly (Diptera: ) Attacking the Fire Solenopsis interrupta (: Formicidae) in Northwestern Argentina

LUIS A. CALCATERRA1

USDAÐARS, South American Biological Control Laboratory, Bolivar 1559 (B1686EFA) Hurlingham, Buenos Aires Province, Argentina

Ann. Entomol. Soc. Am. 100(4): 470Ð473 (2007) ABSTRACT A new species of Pseudacteon phorid ßy, Pseudacteon calderensis (Diptera: Phoridae), is described from females attacking worker of Solenopsis interrupta Santschi in Salta and Jujuy provinces, northwestern Argentina. P. calderensis differs from almost all other South American Pseudacteon species by the structure of the female ovipositor. This new species is morphologically similar to Pseudacteon borgmeieri Schmitz, but it differs slightly in the shape of the apex of the ovipositor and differs strongly because of the absence of large and stout ventral hairs under the ovipositor.

KEY WORDS parasitoid, decapitating ßy, , Þre ant, biological control

At least 30 species of the phorid Pseudacteon of complementary species from regions with different Coquillett (Diptera: Phoridae) are parasitoids of environments and climates could increase the breadth Solenopsis (Hymenoptera: Formicidae) Þre ants in the and magnitude of impacts on imported Þre ant pop- New World (Coquillett 1907, Borgmeier 1963, Disney ulations in the (Porter and Gilbert 1994). Twenty-one species attack South American Þre 2004). Fire ants in the Solenopsis saevissima species- ants in the Solenopsis saevissima species-group (Borg- group occur in different regions of South America meier and Prado 1975, Williams 1980, Porter 1998, from the Amazon Basin of , west to both sides of Brown and Morrison 1999, Brown 2000, Pesquero the Andes, and south to 42Њ latitude, in Rõ´o Negro 2000, Porter and Pesquero 2001, Pitts 2002, Brown et al. Province, in Argentina (Pitts 2002, Calcaterra et al. 2003, Calcaterra et al. 2005, Folgarait et al. 2005, Kro- 2007). Pseudacteon ßies have been reported from all of nforst et al. 2007). South America where Solenopsis is found (Folgarait et decapitating ßies are parasitoids of individ- al. 2005; Calcaterra et al. 2005, 2007). Five of 21 known ual workers (Porter 1998). The adult female inserts a species are abundant, and they have a wide geograph- single egg into the ant thorax with a hypodermic- ical distribution, whereas others seem to be restricted shaped ovipositor in a rapid aerial attack. The larva by geography or host species (Calcaterra et al. 2005, migrates into the head capsule of the worker, where Folgarait et al. 2005). Most of the surveys for ßies were it completes three instars. Just before pupation, the concentrated in a few areas next to large cities (Cal- third instar seems to release an enzyme that causes the caterra et al. 2005). Phorid ßy (and Þre ant) were decapitation of the living host. The pupa completes poorly known from more remote regions, such as development in the head capsule, and the adult ßy western Argentina (Brown et al. 2003; Calcaterra et al. emerges from the oral cavity Ϸ4Ð6 wk after the egg 2005, 2007). That the most recently discovered species was laid, depending on temperature (Porter and Gil- occur in this region (Brown et al. 2003) seems to bert 2004). support the idea that this fauna is among the most Because of their potential as biological control poorly known. In this article, I describe a recently agents, three Þre ant decapitating ßies (Pseudacteon discovered Pseudacteon species in northwestern Ar- tricuspis Borgmeier, Pseudacteon curvatus Borgmeier, gentina (Calcaterra et al. 2005). and Pseudacteon litoralis Borgmeier) have been re- leased against the imported Þre ants Solenopsis invicta Materials and Methods Buren and Solenopsis invicta richteri Forel in the United States, whereas others are being evaluated for Fire ant colonies were disturbed to attract ßies. Fly future release (Porter and Gilbert 2004). The release specimens were collected using a hand aspirator and preserved in 80% ethanol. Fire ant worker samples 1 Corresponding author, e-mail: [email protected] or were collected in 96% ethanol for morphological iden- [email protected]. tiÞcations (King and Porter 2004). Morphological tax-

0013-8746/07/0470Ð0473$04.00/0 ᭧ 2007 Entomological Society of America July 2007 CALCATERRA:ANEW Pseudacteon SPECIES ATTACKING FIRE ANTS 471 onomy of the ants was supplemented with gas chro- of large and stout ventral hairs (Fig. 4); sixth ab- matographic analysis of cuticular hydrocarbons and dominal tergite with 10 hairs (Fig. 5). Ovipositor venom (Vander Meer and Lofgren 1988). simple compressed laterally (Fig. 5), curved in lat- The geographic position and altitude were recorded eral view because dorsal surface truncated and di- using a global positioning system unit Garmin III rected ventrally (Fig. 6); dorsally with small, (Garmin, Olathe, KS). Temperature and humidity also tongue-shaped membranous extension of chitin were recorded when collecting the ßies. near terminus, from which are noted two ßattened Specimens of the new Pseudacteon species have setae (Fig. 6). been deposited at the Museo Argentino de Ciencias Naturales, Bernardino Rivadavia (MACN), Buenos Key to New Pseudacteon Species Aires, and the South American Biological Control Lab- oratory (SABCL), USDAÐARS, Hurlingham, Buenos The key of Porter and Pesquero (2001) to Pseudac- Aires Province, Argentina. Voucher ants are deposited teon species was slightly modiÞed to insert P. calder- at the SABCL. ensis as follow: 5 (3) Ovipositor long, curved downward, with a large ventral tooth near base; hairs on last Pseudacteon calderensis new species abdominal segment not unusually long. . . Type Material. HOLOTYPE: Ǩ. ARGENTINA: ...... P. curvatus Borgmeier Salta: Rt. 9 near La Caldera, 1,471 m, 23Њ 34.242Ј S, 65Њ Ð Ovipositor short with the dorsal surface trun- 22.520Ј W, 14-IX-2004, L. Calcaterra (SABCL), hov- cated and directed downward; with several ering over S. interrupta Santschi workers [MACN hairs extending out under ovipositor . . . 5A ENT]. 5A (5) Sternite 6 with stout ventral hairs almost as PARATYPES: 2 Ǩ. ARGENTINA: Jujuy: Rt. 1, 7 km long as ovipositor ...... N of Caimancito, 365 m, 23Њ 42.811ЈS, 64Њ 31.961Ј W, ...... P. borgmeieri Schimitz 12-IX-2004, L. Calcaterra (SABCL), hovering over S. Ð Sternite 6 without large and stout hairs interrupta workers (MACN). 1Ǩ, Argentina: Jujuy: Rt. extending under ovipositor ...... 9LaCie´naga dam, El Carmen, 1,190 m, 24Њ 25.725Ј S, ...... P. calderensis n. sp. 65Њ 17.859Ј W, 26-X-2003, L. Calcaterra (SABCL), hov- ering over Solenopsis interrupta workers (SABCL ENT Geographical Distribution. Apparently present #66). 2 Ǩ, Argentina: Salta: Rt. 33, near Chicoana, only in northwestern Argentina. Known only from 1,380 m, 25Њ 05.410Ј S, 65Њ 33.883Ј W, 26-X-2003, L. Jujuy and Salta provinces. This species occurred in Calcaterra (SABCL), hovering over S. interrupta sites between 365 and 1,471 m in altitude in workers (SABCL ENT#67). the transition zone between the Chaco, a mosaic of Species Recognition. This species is recognized by ecosystems combining woods with savanna, and Las the diagnostic shape of the ovipositor, which is similar to Yungas, a large area of mountain rain in the that of only two other species, Pseudacteon borgmeieri southern Andes (Cabrera and Willink 1980). The Yun- Schmitz and Pseudacteon solenopsidis (Schmitz). Al- gas are loosely bordered to east by the Chaco phyto- though the shape of the apex of the ovipositor of the six geographical province and tightly interdigitated to the individuals collected was slightly closer to P. borgmeieri west with Bolivian Montane, a dry Forest spanning than P. solenopsidis, the dorsal-posterior surface of the southwestern Bolivia and northwestern Argentina ovipositor has shorter hairs than P. borgmeieri. All spec- (Olson et al. 2001). The annual rainfall in the four imens had six pairs of ventral hairs or setae on sternite 6, collecting sites where the ßies were found is Ϸ600Ð as in P. borgmeieri (P. solenopsidis has only two pairs); 650 mm (De Fina 1992). however, the seventh and eighth pair of large and stout Derivation of Specific Epithet. Calderensis refers to ventral hairs that characterize P. borgmeieri were absent. La Caldera (the boiler), the name of the locality Thus, this species can be easily recognized by its simple, where the holotype of this new species was found. short, and curved ovipositor; short dorsal hairs on the Biology and Behavior. Pseudacteon calderensis was ovipositor; and the absence of large and stout hairs on only found attacking S. interrupta workers in four sternite 6. places and in very low abundance (Calcaterra et al. Description (Female Only; Male Unknown). Lat- 2005). Only six females were captured from four S. eral view of the adult female (Fig. 1). Body length interrupta nests between 1330 and 1830 hours. P. cal- 1.00Ð1.24 mm. Body color brown; frons and tergites derensis females were observed to harass worker ants darker; legs yellowish brown; palpus yellow; halter for several seconds before attempting oviposition, ßy- whitish yellow. Flagellomere 1 ßat and conical; ing in front of the worker and even bumping into the arista present, subequal in length to ßagellomere 1 ant. The temperature and relative humidity when ßies (Fig. 2). Frons with one pair of supra-antennal setae were collected were between 21 and 29ЊC and 23 and and 2-2-4-4 frontal setae. Maximal thorax width 66%, respectively. 0.41Ð0.51 mm; scutellum with two pairs of setae, the The scarcity of the new species could be explained by anterior approximately two thirds the length of the a behavior that is probably similar to the second mor- posterior. Wing vein R2 ϩ 3 absent. Sixth abdominal phologically more similar species, P. solenopsidis, which sternite large with six pairs of setae (Fig. 3) as P. is not attracted to disturbed colonies (Orr et al. 1997, borgmeieri, but without the seventh and eighth pair Wuellner et al. 2002, Calcaterra et al. 2005). The females 472 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 100, no. 4

Fig. 1–6. P. calderensis, new species. (1) Full lateral view of adult ßy. (2) Fronto-lateral view of the female head showing 2-2-4-4 pattern of bristles. (3) Lateral view of the sternite 6 without the large and stout hairs characteristic of P. borgmeieri. (4) Pseudacteon borgmeieri, lateral view (photo by S. Porter). (5) Dorsal posterior view of the sixth abdominal tergite with 10 hairs, and the female ovipositor. (6) Lateral view of the female ovipositor. of P. solenopsidis are not detected when the mounds are P. calderensis could have been underestimated because surveyed for ßies because they usually attack isolated Þre only mounds were surveyed during our surveys. ant foragers probably responding to trail S. interrupta and secondarily Solenopsis electra Forel (Morrison and King 2004). Thus, the new species could have been mentioned as the two most common Þre ant be genetically closer to P. solenopsidis than to P. borg- species occurring in northwestern Argentina (Pitts meieri. If this assumption is conÞrmed, the occurrence of 2002). However, the only Þre ant species found in the July 2007 CALCATERRA:ANEW Pseudacteon SPECIES ATTACKING FIRE ANTS 473 areas where P. calderensis occurred was S. interrupta. Disney, R.H.L. 1994. Scuttle ßies: the Phoridae. Chapman & A third species, the red imported Þre ant S. invicta, is Hall, London, United Kingdom. present within a few kilometers to the east of sites Folgarait, P. J., O. Bruzzone, S. D. Porter, M. A. Pesquero, and where P. calderensis occurred in Salta (Cook et al. L. E. Gilbert. 2005. Biogeography and macroecology of 2004; L.A.C., unpublished data). phorid ßies that attack Þre ants in southeastern Brazil and Argentina. J. Biogeogr. 32: 353Ð367. King, J. R., and S. D. Porter. 2004. Recommendations on the use of alcohols for preservation of ant specimens Acknowledgments (Hymenoptera: Formicidae). Insectes Soc. 51: 1Ð6. Kronforst, M. R., P. J. Folgarait, R.J.W. Patrock, and L. E. We thank Joaquõ´n Sacco and Mariana Emiliozzi (Univer- Gilbert. 2007. Genetic differentiation between body sidad de Buenos Aires) for assistance during Þeld collections, size biotypes of the parasitoid ßy Pseudacteon obtusus Alejandro Reynoso (Comisio´n de Investigaciones Tecnolo´gi- (Diptera: Phoridae). Mol. Phylogenet. Evol. (in press). cas y Espaciales de las Fuerzas Armadas) for photographing Morrison, L. W., and J. R. King. 2004. Host location behav- the ßies used in this work, Sanford Porter for providing Fig. ior in a parasitoid of imported Þre ants. J. Behav. 4; and Cristina Herna´ndez for invaluable advice. We also 17: 367Ð383. thank Brian Brown, Neil Tsutsui, Sanford Porter, and Juan Olson, D. M., E. Dinerstein, E. D. Wikramanayake, N. D. Briano for valuable comments and suggestions that helped to Burgess, G.V.N. Powell, E. C. Underwood, J. A. D’amico, improve the manuscript. I. Itoua, H. E. Strand, J. C. Morrison, et al. 2001. 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