The red imported fire ant (Hymenoptera: Formicidae) in the West Indies: distribution of natural enemies and a possible test bed for release of self-sustaining biocontrol agents.
In South America, fire ant population densities are generally 10 to 20% of invasive populations found in North America (Porter et al. 1992, 1997). Although several hypotheses have been posited to explain the intercontinental differences (Wilder et al. 2012), the most widely accepted is that S. invicta has escaped its natural enemies during founding events (Porter et al. 1997). Classical or self-sustaining biological control agents from South America are important components of a biological control program because they offer the possibility for permanent, regional suppression of fire ants (Williams et al. 2003). At least 44 fire ant natural enemies have been identified in South America: Pseudacteon fly parasitoids (23 species), microsporidia (Vairimorpha invictae and Kneallhazia solenopsae),fungus (Myrmecomyces annellisae), nematodes (Allomermis solenopsi, Tetradonema solenopsis, and Hexamerma spp.), eucharitid wasps (5 species), scarab beetle (Martineziana dutertrei), strepsipteran (Caenocholax fenyesi), parasitic ant (Solenopsis daguerrei), densovirus (Solenopsis invicta densovirus, SiDNV), and RNA viruses (3 viruses) (Wojcik et al. 1987; Williams et al. 2003; Briano et al. 2012). By way of comparison, only 6 natural enemies have been found in the United States: the microsporidian K. solenopsae, the Martineziana scarab beetle, the Caenocholax strepsipteran, and 3 RNA viruses as above (Wojcik et al. 1987; Williams et al. 2003; Briano et al. 2012). Successful releases of self-sustaining parasites and pathogens will not eradicate fire ants but could help tilt the ecological balance in favor of native arthropods (Porter 1998). If this happens, fire ant populations in introduced ranges could be reduced to levels similar to those in South America where fire ants are not considered an important problem (Porter et al. 1997).
The S. invicta infestation in the West Indies offers excellent opportunities to examine and quantify the effectiveness of specific natural enemies, alone or in combination, on S. invicta populations. The islands are relatively small, making biological control efforts (introductions and evaluations) manageable. Because the S. invicta populations established on each of these islands represent separate and unique infestations, the first task is to screen the populations of S. invicta for known pathogens. Thus, our objective was to conduct a survey for the presence of pathogens among S. invicta populations of many of the islands of the West Indies in which S. invicta is established.
Materials and Methods
Solenopsis invicta workers were sampled by hand-collecting ants from nest mounds and attracting ants to tuna lures during surveys of fire ant distribution in the Caribbean (Wetterer & Snelling 2006; Wetterer & Davis 2010; Wetterer et al. 2014). The ants were placed in 99% ethanol. Detailed collection notes for all samples evaluated are provided in the Supplementary Material for this article in Florida Entomologist 98(4) (Dec 2015) online (http://purl.fcla.edu/fcla/entomologist/ browse). Red imported fire ant workers (S. invicta) were discriminated from native tropical fire ant workers (Solenopsis geminata [F.]) by the isometry of large workers compared with small workers and by the presence of a medial clypeal tooth in minor workers (Wojcik et al. 1976).
Pathogen/parasite infections were determined by molecular methods because they offer the most sensitive approach for detection. Solenopsis invicta ant samples were first processed to extract RNA by the Trizol (Invitrogen, Thermo Fisher Scientific, Waltham, Massachusetts, USA) method and DNA by a method described previously (Valles et al. 2002). A pooled sample of 10 worker ants was used for each nucleic acid preparation. In some cases, fewer ants were available. In these instances, the ants were divided in half for each preparation (DNA and RNA). DNA was used as template to conduct polymerase chain reaction (PCR) to determine the social form of the ants by genotyping the Gp-9 alleles (Valles & Porter 2003), and to detect the presence of K. solenopsae (Valles et al. 2002), V. invictae (Valles et al. 2004), SiDNV (Valles et al. 2013b), and Pseudacteon decapitating parasitic flies (Oi et al. 2009). RNA from each sample was evaluated by reverse transcriptase PCR (RT PCR) for the presence of Solenopsis invicta viruses SINV-1, SINV-2, and SINV-3 (Valles et al. 2009). Retrospective screening for these viruses in ant samples stored in ethanol is possible for years after collection (Valles 2007; S. M. V., unpubl. data).
Samples testing positive by generation of an amplicon of anticipated size were repeated to ensure that the result was not a false positive. In addition, gel-purified amplicons were ligated into the pCR4-TOPO vector, transformed into TOP10 competent cells (Invitrogen, Thermo Fisher Scientific, Waltham, Massachusetts, USA) and sequenced at the Interdisciplinary Center for Biotechnology Research (University of Florida, Gainesville, Florida, USA) by the Sanger method to verify that the amplicon was from the suspected pathogen or parasite. Sequences were analyzed by Blast analysis to establish their identity (Altschul et al. 1997).
Results and Discussion
In total, 254 S. invicta samples were collected from across the West Indies; the ants were genotyped at the Gp-9 locus to assign social form and evaluated by molecular methods for the presence of key pathogens and parasites. Monogyny, or single-queen colonies, was the most prevalent social form, representing 65% (182/254) of the samples. This percentage was less than in most areas in the United States (80-85%, Porter 1992; Porter et al. 1992, 1997) and South America (~90%, Porter et al. 1997) but more than in Texas (~50%, Porter et al. 1991). Because monogyne and polygyne colonies are genetically distinct, it is somewhat surprising that 80% of the islands surveyed had both polygyne and monogyne fire ants present (16/20; Fig. 1). Only the monogyne social form was detected on Aruba, Barbuda, Grand Cayman, and Jamaica (Fig. 1). Conversely, only polygyne colonies were detected on Great Stirrup Cay. However, of sites with only one social form, only Barbuda had enough samples to expect the possibility of finding both forms. Also consider that the ant samples collected at lures were pooled for analysis and likely represented a mixture of colonies. A single polygyne ant included in this sampling method would mask any workers from monogyne colonies included in the samples. Thus, monogyny may be under-represented with this sampling method.
Regardless, the high frequency of both social forms on these islands suggests two possibilities. First, most islands experienced multiple independent invasions of each social form. This possibility seems a bit unlikely, but monogyne queens may be able to disperse long distances (20-30 km) on wind currents after mating 50 to 100 m in the air (Vinson & Greenberg 1986), and the polygyne social form may have spread via island-to-island transport of infested nursery stock or other commercial products in contact with soil; alate polygnye queens are rather feeble and do not easily found independent claustral colonies (Preston et al. 2007). The second, intriguing possibility for the high frequency of both social forms is that most dispersal occurs from inter-island transport of polygyne colonies, and heterozygous polygyne queens are capable of producing homozygous monogyne populations. Genetic analyses among colonies on these islands could discern their relatedness and provide insight into the introduction and spread of S. invicta on these islands (Ascunce et al. 2010). The answer to this question also would help establish whether long-distance transport of monogyne queens after mating flights has been an important mechanism in the invasion and dispersal of S. invicta across the West Indies. A better understanding of the mechanisms of inter-island invasions could be useful in restricting the dispersal of this pest among islands or island groups in the Pacific.
Our tests detected the presence of 2 microsporidian pathogens and 2 fire ant viruses. The microsporidian K. solenopsae was detected and verified from 20 S. invicta samples collected from 10 of the 20 islands, including Anguilla, Antigua, Great Stirrup Cay, New Providence, St. Kitts, St. Croix, St. Martin, St. Thomas, Tortola, and Trinidad. The majority of these infections (15/20) were detected in polygyne colonies, which is consistent with pathogen surveys conducted in the United Sates (Oi et al. 2004; Valles et al. 2010; Allen et al. 2011).
Two monogyne samples from New Providence tested positive for SINV-1. SINV-1 exhibits widespread distribution in U.S. and South American fire ant populations and is sometimes very prevalent in localized populations (often >80%) (Valles et al. 2009; Valles 2012). This virus often accompanies founding populations (Yang et al. 2010).
Another microsporidian species, V. invictae, was shown to be present in a polygyne sample collected from St. Croix. Vairimorpha invictae is limited to S. invicta populations in its native range (Oi et al. 2012), so this is the first detection of this pathogen outside South America. Curiously, we also found the virus SiDNV in 1 polygyne sample from Anguilla. SiDNV is also not found in S. invicta U.S. populations (Valles et al. 2013b), so detection of this virus on Anguilla represents a new geographic discovery. The presence of V. invictae in St. Croix and SiDNV in Anguilla suggests some fire ants in the West Indies may originate directly from South America rather than from introduced U.S. populations. Another possibility that needs to be investigated is that these pathogens jumped from the tropical fire ant (S. geminata) populations, which are common in the West Indies, or that the 2 samples in question may have included a few S. geminata workers by accident. The problem with this hypothesis is that V. invictae has not been detected in S. geminata (Oi et al. 2010) and we do not know whether S. geminata is capable of serving as a host for SiDNV.
The absence of SINV-2 and SINV-3 in West Indies S. invicta samples is of considerable interest because it suggests that these 2 pathogens, and some of the pathogens above, could be released in the West Indies as self-sustaining biological control agents. These viruses have been reported to be absent in founding populations in China, California, and Australia (Yang et al. 2010). We are particularly interested in the possibility of releasing SINV-3 because laboratory studies have shown it to be highly pathogenic, virulent, and host specific to fire ants in the saevissima complex from South America (Porter et al. 2013, 2015).
DNA evidence of Pseudacteon decapitating flies was found in 1 ant sample from Great Stirrup Cay. This result was confirmed by collection of an adult female Pseudacteon curvatus Borgmeier fly from this location. In addition, 2 P curvatus females and 1 male Pseudacteon tricuspis Borgmeier fly were collected from New Providence Island about 100 km to the southeast. The discovery of these flies was surprising because the collection sites were separated by 100 to 200 km of open sea from mainland Florida where P. curvatus and P tricuspis had been released 8 and 11 yr earlier, respectively. Bulk transport of parasitized fire ants in nursery plants from Florida or transport by large wind storms are possible explanations for their presence on these 2 islands. The absence of DNA evidence of flies from other samples was expected because these samples were all collected in years and at locations not likely to have been exposed to Pseudacteon parasitoids.
As hypothesized, the introduction(s) of S. invicta onto the islands of the West Indies occurred largely without accompanying natural enemies. No natural enemies were detected on half of the islands examined, and on the remaining islands, S. invicta populations supported only 1 or 2 natural enemies. These data provide further support for the hypothesis that escape from natural enemies contributes to the successful invasive capacity of this ant (Porter et al. 1992). Lack of natural enemies within these discrete populations and the relatively small, isolated nature of the islands indicate that they may serve as suitable test locations for the intentional introduction and subsequent evaluation of natural enemies against S. invicta. The isolated habitat offers the ability to quantify the impact of different natural enemies alone, or in combination, on S. invicta populations in a relatively short time frame. Additionally, introductions can be more closely monitored providing a better understanding of the epidemiology in the case of pathogens.
The successful utilization of islands for this purpose has been reported for a number of invertebrate invasive pests. One of the best documented examples is the rhinoceros beetle (Oryctes rhinoceros [L.]; Coleoptera: Dynastidae) in the South Pacific (Young 1986). A baculovirus was discovered in the beetle, but there was doubt about the impact of this virus on the beetle population (Marschall 1970). However, carefully planned and executed introductions into beetle populations onto Tongatapu and certain islands of Fiji resulted in an epizootic and corresponding decline in the beetle populations (Young 1974; Bedford 1976). The researchers introduced the virus onto one side of the island and were able to follow its spread and estimate the rate of spread of the epizootic across to the other side. Island biological control efforts have been reported also for Schizophora flies on Easter Island (Ripa et al. 1995) and Schistosoma snails in the Caribbean (Pointier & McCullough 1989).
Laboratory tests have shown that SINV-3 causes significant mortality in S. invicta colonies (Porter et al. 2013; Valles et al. 2014). SINV-3--treated colonies suffer collapse and elimination within 30 to 60 d of infection depending on the virulence of the strain (Valles et al. 2013a). Successful field releases of SINV-3 have been accomplished in Florida (Valles & Oi 2014) and introductions established in California (S. M. V. and D. H. Oi, unpublished results). However, the impact of the virus on the S. invicta field population has not been determined. Our goal is to release SINV-3 alone or in combination with other S. invicta natural enemies (SiDNV, V invictae, SINV-1, SINV-2, Pseudacteon species) into the ant populations on islands of the West Indies and monitor the impact and spread of the agents. The data reported in this study demonstrate the suitability of these islands to study S. invicta biological control under controlled conditions.
We thank David Oi and James Becnel (USDA-ARS) for critical reviews of the manuscript, Jenny Slone (USDA-ARS) for translating the abstract, and Chuck Strong (USDA-ARS) for conducting the molecular assays. The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the United States Department of Agriculture or the Agricultural Research Service of any product or service to the exclusion of others that may be suitable.
Allen C, Valles SM, Strong CA. 2011. Multiple virus infections occur in individual polygyne and monogyne Solenopsis invicta ants. Journal of Invertebrate Pathology 107: 107-111.
Altschul SF, Madden TL, Schaffer AA, Zhang J, Zhang Z, Miller W, Lipman DJ. 1997. Gapped BLAST and PSI-BLAST: a new generation of protein database search programs. Nucleic Acids Research 25: 3389-3402.
Ascunce MS, Valles SM, Oi DH, Shoemaker D, Plowes R, Gilbert L, LeBrun EG, Sanchez-Arroyo H, Sanchez-Pena S. 2010. Molecular diversity of the microsporidium Kneallhazia solenopsae reveals an expanded host range among fire ants in North America. Journal of Invertebrate Pathology 105: 279-288.
Bedford GO. 1976. Use of a virus against the coconut palm rhinoceros beetle in Fiji. Proceedings of the National Academy of Sciences 22: 11-25.
Briano J, Calcaterra L, Varone L. 2012. Fire ants (Solenopsis spp.) and their natural enemies in southern South America. Psyche 2012: Article ID 198084, 1-19.
Callcott AM, Collins HL. 1996. Invasion and range expansion of imported fire ants (Hymenoptera: Formicidae) in North America from 1918-1995. Florida Entomologist 79: 240-251.
Collins HL, Callcott AM, Lockley TC, Ladner A. 1992. Seasonal trends in effectiveness of hydramethylnon (AMDRO) and fenoxycarb (LOGIC) for control of red imported fire ants (Hymenoptera: Formicidae). Journal of Economic Entomology 85: 2131-2137.
Davis LR, Vander Meer RK, Porter SD. 2001. Red imported fire ants expand their range across the West Indies. Florida Entomologist 84: 735-736.
Drees BM, Barr CL, Vinson SB, Gold RE, Merchant ME, Riggs N, Lennon L, Russell S, Nester P, Kostroun D, Flanders K, Sparks B, Horton PM, Pollet D, Oi D, Shanklin D, Loftin K, Koehler PL, Vail K, Vogt JT. 2009. Managing imported fire ants in urban areas. Bulletin 1191. University of Georgia, Athens, Georgia, USA.
Marschall KJ. 1970. Introduction of a new virus disease of the coconut rhinoceros beetle in Western Samoa. Nature 225: 288-289.
Oi DH, Valles SM, Pereira RM. 2004. Prevalence of Thelohania solenopsae (Microsporidia: Thelohaniidae) infection in monogyne and polygyne red imported fire ants (Hymenoptera: Formicidae). Environmental Entomology 33: 340-345.
Oi DH, Porter SD, Valles SM, Briano JA, Calcaterra LA. 2009. Pseudacteon decapitating flies (Diptera: Phoridae): Are they potential vectors of the fire ant pathogens Kneallhazia (=Thelohania) solenopsae (Microsporidia: Thelohaniidae) and Vairimorpha invictae (Microsporidia: Burenellidae)? Biological Control 48: 310-315.
Oi DH, Valles SM, Briano J. 2010. Laboratory host specificity testing of the fire ant microsporidium pathogen Vairimorpha invictae (Microsporidia: Burenellidae). Biological Control 53: 331-336.
Oi DH, Valles SM, Porter SD. 2012. The fire ant pathogen Vairimorpha invictae (Microsporidia: Burenellidae) not detected in Florida. Florida Entomologist 95: 506-508.
Pereira RM. 2003. Areawide suppression of fire ant populations in pastures: project update. Journal of Agricultural and Urban Entomology 20: 123-130.
Pointier JP, McCullough F. 1989. Biological control of the snail hosts of Schistosoma mansoni in the Caribbean area using Thira spp. Acta Tropica 46: 147-155.
Porter SD. 1992. Frequency and distribution of polygyne fire ants (Hymenoptera: Formicidae) in Florida. Florida Entomologist 75: 248-257.
Porter SD. 1998. Biology and behavior of Pseudacteon decapitating flies (Diptera: Phoridae) that parasitize Solenopsis fire ants (Hymenoptera: Formicidae). Florida Entomologist 81: 292-309.
Porter SD, Bhatkar AP, Mulder R, Vinson SB, Clair DJ. 1991. Distribution and density of polygyne fire ants (Hymenoptera: Formicidae) in Texas. Journal of Economic Entomology 84: 866-874.
Porter SD, Fowler HG, Mackay WP. 1992. Fire ant mound densities in the United States and Brazil (Hymenoptera: Formicidae). Journal of Economic Entomology 85: 1154-1161.
Porter SD, Williams DF, Patterson RS, Fowler HG. 1997. Intercontinental differences in the abundance of Solenopsis fire ants (Hymenoptera: Formicidae): escape from natural enemies? Environmental Entomology 26: 373-384.
Porter SD, Valles SM, Oi DH. 2013. Host specificity and colony impacts of Solenopsis invicta virus 3. Journal of Invertebrate Pathology 114: 1-6.
Porter SD, Valles SM, Wild AL, Dieckmann R, Plowes NJR. 2015. Solenopsis invicta virus 3: Further host-specificity tests with native Solenopsis ants (Hymenoptera: Formicidae). Florida Entomologist 98: 122-125.
Preston CA, Fritz GN, Vander Meer RK. 2007. Prevalence of Thelohania solenopsae infected Solenopsis invicta newly mated queens within areas of differing social form distributions. Journal of Invertebrate Pathology 94: 119-124.
Ripa SR, Rojas PS, Velasco G. 1995. Releases of biological control agents of insect pests on Easter Island (Pacific Ocean). Entomophaga 40: 427-440.
Valles SM. 2007. Ethanol preservation of fire ants allows retrospective screening for Solenopsis invicta virus-1. Florida Entomologist 90: 577-578.
Valles SM. 2012. Positive-strand RNA viruses infecting the red imported fire ant, Solenopsis invicta. Psyche 2012: Article ID 821591, 1-14.
Valles SM, Oi DH. 2014. Successful transmission of Solenopsis invicta virus 3 to field colonies of Solenopsis invicta (Hymenoptera: Formicidae). Florida Entomologist 97: 1244-1246.
Valles SM, Porter SD. 2003. Identification of polygyne and monogyne fire ant colonies (Solenopsis invicta) by multiplex PCR of Gp-9 alleles. Insectes Sociaux 50: 199-200.
Valles SM, Oi DH, Perera OP, Williams DF. 2002. Detection of Thelohania solenopsae (Microsporidia: Thelohaniidae) in Solenopsis invicta (Hymenoptera: Formicidae) by multiplex PCR. Journal of Invertebrate Pathology 81: 196-201.
Valles SM, Oi DH, Briano JA, Williams DF. 2004. Simultaneous detection of Vairimorpha invictae (Microsporidia: Burenellidae) and Thelohania solenopsae (Microsporidia: Thelohaniidae) in fire ants by PCR. Florida Entomologist 87: 85-87.
Valles SM, Varone L, Ramirez L, Briano J. 2009. Multiplex detection of Solenopsis invicta viruses -1, -2, and -3. Journal of Virological Methods 162: 276-279.
Valles SM, Oi DH, Porter SD. 2010. Seasonal variation and the co-occurrence of four pathogens and a group of parasites among monogyne and polygyne fire ant colonies. Biological Control 54: 342-348.
Valles SM, Porter SD, Choi MY, Oi DH. 2013a. Successful transmission of Solenopsis invicta virus 3 to Solenopsis invicta fire ant colonies in oil, sugar, and cricket bait formulations. Journal of Invertebrate Pathology 113: 198-204.
Valles SM, Shoemaker D, Wurm Y, Strong CA, Varone L, Becnel JJ, Shirk PD. 2013b. Discovery and molecular characterization of an ambisense densovirus from South American populations of Solenopsis invicta. Biological Control 67: 431-439.
Valles SM, Porter SD, Firth AE. 2014. Solenopsis invicta virus 3: pathogenesis and stage specificity in red imported fire ants. Virology 461: 66-71.
Vinson SB, Greenberg L. 1986. The biology, physiology, and ecology of imported fire ants, pp. 193-226 In Vinson SB [ed.], Economic Impact and Control of Social Insects. Praeger Scientific, New York, New York USA.
Wetterer JK, Davis LR. 2010. Solenopsis invicta (Hymenoptera: Formicidae) in the Lesser Antilles. Florida Entomologist 93: 128-129.
Wetterer JK, Snelling RR. 2006. The red imported fire ant, Solenopsis invicta, in the Virgin Islands (Hymenoptera: Formicidae). Florida Entomologist 89: 431-434.
Wetterer J, Davis Jr L, White G. 2014. Spread in Trinidad of the South American fire ant Solenopsis invicta (Hymenoptera, Formicidae). Florida Entomologist 97: 238-241.
Wilder SM, Barnum TR, Holway DA, Suarez AV, Eubanks MD. 2012. Introduced fire ants can exclude native ants from critical mutualist-provided resources. Oecologia 172: 197-205.
Williams DF, Collins HL, Oi DH. 2001. The red imported fire ant (Hymenoptera: Formicidae): an historical perspective of treatment programs and the development of chemical baits for control. American Entomologist 47: 146-159.
Williams DF, Oi DH, Porter SD, Pereira RM, Briano JA. 2003. Biological control of imported fire ants (Hymenoptera: Formicidae). American Entomologist 49: 150-163.
Wojcik DP, Buren WF, Grissell EE, Carlysle T. 1976. The fire ants (Solenopsis) of Florida (Hymenoptera: Formicidae). Entomology Circular No.173. Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Gainesville, Florida, USA.
Wojcik DP, Jouvenaz DP, Banks WA. 1987. Biological control agents of fire ants in Brazil, pp. 627-628 In Eder J, Rembold H [eds.], Chemistry and Biology of Social Insects. Peperny, Munich, Germany.
Yang CC, Yu YC, Valles SM, Oi DH, Chen YC, Shoemaker D, Wu WJ, Shih CJ. 2010. Loss of microbial (pathogen) infections associated with recent invasions of the red imported fire ant Solenopsis invicta. Biological Invasions 12: 33073318.
Young EC. 1974. The epizootiology of two pathogens of the coconut palm rhinoceros beetle. Journal of Invertebrate Pathology 24: 82-92.
Young EC. 1986. The rhinoceros beetle project: history and review of the research programme. Agriculture, Ecosystems and Environment 15: 149-166.
Zakharov AA, Thompson LC. 1998. Effects of repeated use of fenoxycarb and hydramethylnon baits on nontarget ants. Journal of Entomological Science 33: 212-220.
Caption: Fig. 1. Distribution of 2 fire ant microsporidian pathogens (Kneallhazia solenopsae, Vairimorpha invictae) and 2 fire ant viruses (SINV-1, SiDNV) among collections of the red imported fire ant, Solenopsis invicta, from islands in the West Indies. The fire ant RNA viruses SINV-2 and SINV-3 were not detected in any of the collections. The number of collections from monogyne colonies is shown over the total number of collections for each island or island group (Tortola [1/5], St. John [0/1], and St. Thomas [3/4]).
Steven M. Valles (1) *, James K. Wetterer (2), and Sanford D. Porter (1)
(1) Center for Medical, Agricultural and Veterinary Entomology, USDA-ARS, 1600 SW 23rd Drive, Gainesville, Florida 32608, USA
(2) Wilkes Honors College, Florida Atlantic University, 5353 Parkside Drive, Jupiter, Florida 33458, USA
* Corresponding author; E-mail: firstname.lastname@example.org
Supplementary material for this article in Florida Entomologist 98(4) (Dec 2015) is online at http://purl.fcla.edu/fcla/entomologist/browse
Please note: Some tables or figures were omitted from this article.
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||Research Papers|
|Author:||Valles, Steven M.; Wetterer, James K.; Porter, Sanford D.|
|Date:||Dec 1, 2015|
|Previous Article:||Five new species of Phyllophaga (Coleoptera: Melolonthidae) of northwestern Mexico.|
|Next Article:||Sucrose triggers honeydew preference in the ghost ant, Tapinoma melanocephalum (Hymenoptera: Formicidae).|