DOI: 10.13102/sociobiology.v60i4.484-486Sociobiology 60(4): 484-486 (2013) Open access journal: http://periodicos.uefs.br/ojs/index.php/sociobiology ISSN: 0361-6525 Laboratory Rearing and Niche Resources of Pseudacteon spp. Coquillett (Diptera: Phoridae) Parasitoids of Solenopsis saevissima (Smith) (Hymenoptera: Formicidae) ma pesquero, apa vaz, fv arruda The fire ants Solenopsis invicta Buren and Solenopsis saevissima (Smith) have wide distribution in South America (Trager, 1991). The workers of these species are aggressive and have a painful sting, with the colonies located on the surface of the soil, thus increasing the chances of accidents with people. After the inadvertent introduction in the United States, S. invicta has victimized thousands of people, includ- ing records of deaths from anaphylactic shock (Caldwell et al., 1999). The geographical distribution in the central region of South America may have reduced the risk of dispersal of S. saevissima to other countries via sea transport, as was probably the case with S. invicta from northern Argentina in the United States (Caldera et al., 2008). However, urban ar- eas infested with S. saevissima were reported in the Amazon region (Brazil, 2008), suggesting the possibility of this spe- cies becoming a pest, and previous efforts to establish con- trol strategies are important in preventing damage, whether it be economic, ecological or health related. In Brazil, nine parasitoids species of Pseudacteon Coquillett are associated with S. saevissima (Pesquero & Dias, 2011). Confirmation of parasitism by these species is important for future biological Abstract Solenopsis saevissima (Smith) is associated with a group of nine Pseudacteon Co- quillett species in Brazil. Adult female flies of Pseudacteon affinis Borgmeier, Pseu- dacteon dentiger Borgmeier and Pseudacteon disneyi Pesquero were created in a laboratory from parasitized workers of S. saevissima. The initial development of Pseudacteon cultellatus Borgmeier was faster than the other phorid species, taking 12 days to kill the host workers. Similar to the group of phorid species parasitizing Solenopsis invicta Buren, the daily period of activity and body size are important factors to be considered in the use of these natural enemies in future programs of biological control of S. saevissima. Sociobiology An international journal on social insects Universidade Estadual de Goiás, Morrinhos, Goiás, Brazil SHORT NOTE Article History Edited by: Evandro N Silva, UEFS, Brazil Received 26 July 2013 Initial acceptance 07 September 2013 Final acceptance 02 October 2013 Keywords Community, Biological control, Fire ant Brazil Corresponding author Marcos Antônio Pesquero Universidade Estadual de Goiás Unidade Universitária de Morrinhos Rua 14, 625. Jardim América. Morrinhos, Goiás, Brazil CEP 75.650-000 E-Mail: mapesq@ueg.br control programs of S. saevissima, but it still remains un- known for many Pseudacteon species. Thus, the aim of this study was to describe seasonality and body size distribution for understanding the Pseudacteon community structure as- sociated with S. saevissima and to prove the parasitism in a laboratory. This study was conducted in the municipalities of Goiânia and Morrinhos, Goiás, Brazil, in the region original- ly occupied by Cerrado and dominated by cattle and soybean. Data on the abundance of parasitoids and air temperature were obtained monthly in one-hour intervals throughout the day period, from Sep/2010 to Aug/2011, in eight sites sur- rounding the urban area. All the mounds of the fire ants were counted and disturbed to attract parasitoids which were col- lected, identified (Porter & Pesquero, 2001) and transferred for closed trays containing 5g of workers of S. saevissima maintained in quarantine for 45 days. A maximum of five individuals of the same species were transferred per tray for two hours, totaling up to 30 individuals of each Pseudacteon species. These trays with parasitized ants were later taken to the laboratory and kept in a climatic chamber under con- Sociobiology 60(4): 484-486 (2013) 493 trolled temperature (24 °C), photoperiod (12:12 h) and hu- midity (40-60%). The trays were checked daily to record the development of parasitoids. A maximum of 30 individuals of each parasitoid species were sacrificed for size measure- ments (length of hind tibia). The density of fire ant mounds, all identified as S. sae- vissima, was 37.5 ± 3.0 mounds/ha (n = 8). We captured 314 female flies on the 56 fire ant mounds identified as P. affinis (26.75%), P. cultellatus (24.52%), P. disneyi (16.56%), P. dentiger (14.65%), P. nudicornis (7%), the small biotype P. tricuspis (4.14%), P. fowleri (1.91%) and P. lenkoi (1.27%). Ten individuals (3.18%) of P. solenopsidis were observed attacking workers on fire ant trails. The five most abundant species occurred in the eight sites of the two municipalities; P. lenkoi and P. solenopsidis occurred in two sites of the two municipalities; P. fowleri occurred in one site of the two mu- nicipalities and P. tricuspis small biotype occurred in three sites of Goiânia. The four most abundant species were sea- sonally constant throughout the year. With the exception of P. dentiger that has been active in the hottest hours of the day (32.44 ± 0.41 °C, n = 46) (χ2 = 19.58, df = 2, P < 0.00001), P. affinis and P. disneyi were more active during the last hours of the day (χ2 = 23.74 and χ2 = 23.65, df = 2, P < 0.00001, re- spectively), and P. cultellatus was more active during the first hours of the day (χ2 = 33.26, df = 2, P < 0.000001) (Fig 1). Daily activity patterns have been previously described (Pes- quero et al., 1996), suggesting the importance that physical factors have on the niche dimension and coexistence of this group of insects. Similarly, the gradient body size of worker ants seems to be an important resource to be shared among Pseudac- teon species (Fowler, 1997). The body size of the four most abundant species differ significantly (Table 1), and P. affi- nis parasitized larger workers ants compared with P. disneyi (Mann-Whitney test, z = -4.54, P < 0.00001) and P. cultel- latus (Mann-Whitney test, z = -3.06, P < 0.005) (Table 1). However, the worker ants parasitized by P. disneyi and P. cultellatus did not differ statistically. The low relative abun- dance and the small body size of P. tricuspis (Table 1) differ from the observations of Fowler (1977) in southeastern Bra- zil, and these differences suggest the presence of two differ- ent species (Kronforst et al., 2007). With the exception of P. solenopsidis all species of parasitoids found in the study sites attacked workers of S. saevissima in the trays. However, only one individual of P. affinis, P. dentiger and P. disneyi completed the development in the laboratory resulting in adults. It is likely that the high mortality of larvae and pupae was a result of the low rearing conditions (temperature of 24°C and humidity of 40-60%) compared with other studies (Folgarait et al., 2005). The lar- val development time from the adult phorid flies attack to the ant host death was two days faster for P. cultellatus (12 days) compared with P. affinis (Mann-Whitney test, z = -3.40, P < 0.001) and P. disneyi (Mann-Whitney test, z = -3.72, P < 0.001) (Table 1). The larval development period observed for the latter two species (14 days) is similar to that observed for P. obtusus on S. richteri (14,6 days) (Folgarait et al., 2005). Evidence of parasitism for only three of the nine species of Pseudacteon associated with S. saevissima is a technical problem. The elevation of temperature and hu- Pseudacteon Tibia length (mm) mean±SD N Head width of parasitized ants (mm) mean ± SD N Lifetime ant after parasitoid attack (days) N tricuspis * 0.266 ± 0.0223 12 - - - - nudicornis 0.296 ± 0.0202 17 - - - - disneyi 0.296 ± 0.0293 a 30 0.810 ± 0.101 31 14.161 ± 2.238 31 cultellatus 0.339 ± 0.0401 b 30 0.841 ± 0.116 29 12.310 ± 1.366 29 fowleri 0.392 ± 0.0314 06 - - - - affinis 0.426 ± 0.0561 c 30 0.967 ± 0.184 48 14.104 ± 3.019 48 solenopsidis 0.433 ± 0.0258 10 - - - - dentiger 0.471 ± 0.0403 d 30 - - - - lenkoi 0.477 ± 0.0252 04 - - - - * small biotype Table 1. Tibia length of Pseudacteon species; head width of Solenopsis saevissima and lifetime worker ant after parasitoid attack. Only spe- cies with n > 30 were used in the analysis. Means followed by the same letter are not statistically different (F = 121.82, df = 168, P < 0.01. Tukey, P < 0.01). Fig 1. 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