Potential Global Range Expansion of the Invasive Fire Ant, Solenopsis invicta

The red imported fire ant, Solenopsis invicta Buren, is an invasive pest that has become widespread in the southern United States and Caribbean after introduction from South America in the 1930s. This species, which has diverse detrimental impacts on recipient communities, was recently discovered in Australia and New Zealand and has the potential to colonize numerous other regions. We used a dynamic, ecophysiological model of colony growth to predict the potential global range expansion of this invasive species. Based on minimum and maximum daily temperatures, the model estimates colony alate production and predicts future geographic range limits. Because S. invicta populations are limited by arid conditions as well as cold temperatures, we superimposed precipitation data upon temperature-based predictions, to identify regions that do not receive enough rainfall to support this species across the landscape. Many areas around the globe, including large portions of Europe, Asia, Africa, Australia, and numerous island nations, are at risk for S. invicta infestation. Quarantine officials should be vigilant for any accidental introductions of this pest in susceptible regions. Costs of eradication increase dramatically as the area of infestation grows, and large infestations may be impossible to eradicate. Other South American Solenopsis fire ants (e.g., S. richteri Forel) may become invasive if the opportunity arises, and our predictions for S. invicta may approximate the potential range limits for these species as well.     

Expressed sequence tags from the red imported fire ant, Solenopsis invicta: annotation and utilization for discovery of viruses

An expression library was created and 2304 clones sequenced from a monogyne colony of Solenopsis invicta. The primary intention of the project was to utilize homologous gene identification to facilitate discovery of viruses infecting this ant pest that could potentially be used in pest management. Additional genes were identified from the ant host and associated pathogens that serve as an important resource for studying these organisms. After assembly and removal of mitochondrial and poor quality sequences, 1054 unique sequences were yielded and deposited into the GenBank database under Accession Nos. EH412746 through EH413799. At least nine expressed sequence tags (ESTs) were identified as possessing microsatellite motifs and 15 ESTs exhibited significant homology with microsporidian genes. These sequences most likely originated from Thelohania solenopsae, a well-characterized microsporidian that infects S. invicta. Six ESTs exhibited significant homology with single-stranded RNA viruses (3B4, 3F6, 11F1, 12G12, 14D5, and 24C10). Subsequent analysis of these putative viral ESTs revealed that 3B4 was most likely a ribosomal gene of S. invicta, 11F1 was a single-stranded RNA (ssRNA) virus contaminant introduced into the colony from the cricket food source, 12G12 appeared to be a plant-infecting tenuivirus also introduced into the colony as a field contaminant, and 3F6, 14D5, and 24C10 were all from a unique ssRNA virus found to infect S. invicta. The sequencing project illustrates the utility of this method for discovery of viruses and pathogens that may otherwise go undiscovered.     

Molecular Identification of Hemolymph-Associated Symbiotic Bacteria in Red Imported Fire Ant Larvae

The red imported fire ant (RIFA) (Solenopsis invicta Buren), an exotic insect pest in Texas, has become well established throughout the eastern part of the state. More aggressive than native ant species, RIFA gradually have enlarged their range and spread north and west despite intense efforts to stop them. Symbiotic bacteria have an important relationship in the midgut of fourth instar RIFA larvae. However, the presence of symbiotic bacteria in hemolymph has not been explored. In this study, symbiotic bacteria isolated from the hemolymph of fourth instar larvae of RIFA were genetically identified in terms of genus using a partial sequence of the 16S rRNA gene. Using three different primer sets to amplify regions of the gyrA, gyrB, and SG850 genes, multiple species of the genus Bacillus were identified as inhabitants of fire ant hemolymph. Analysis of gyrA gene identified Bacillus cereus with a percentage match of 94.13–99.20% with DNA sequences from GenBank BLAST (). Using the gyrB gene, Bacillus species were identified with a percentage match of 95.48% to 100% using DNA sequences from GenBank. Finally, analysis of the SG850 gene identified Bacillus cereus with a percentage match of 96.20% to 99.83% using DNA sequences from GenBank.     

Habitat alteration increases invasive fire ant abundance to the detriment of amphibians and reptiles

Altered habitats have been suggested to facilitate red imported fire ant (Solenopsis invicta) colonization and dispersal, possibly compounding effects of habitat alteration on native wildlife. In this study, we compared colonization intensity of wood cover boards by S. invicta among four forest management treatments in South Carolina, USA: an unharvested control (>30 years old); a partially thinned stand; a clearcut with coarse woody debris retained; and a clearcut with coarse woody debris removed. Additionally, we compared dehydration rates and survival of recently metamorphosed salamanders (marbled salamanders, Ambystoma opacum, and mole salamanders, A. talpoideum) among treatments. We found that the number of wood cover boards colonized by S. invicta differed significantly among treatments, being lowest in the unharvested forest treatments and increasing with the degree of habitat alteration. Salamanders that were maintained in experimental field enclosures to study water loss were unexpectedly subjected to high levels of S. invicta predation that differed among forest treatments. All known predation by S. invicta was restricted to salamanders in clearcuts. The amount of vegetative ground cover was inversely related to the likelihood of S. invicta predation of salamanders. Our results show that S. invicta abundance increases with habitat disturbance and that this increased abundance has negative consequences for amphibians that remain in altered habitats. Our findings also suggest that the presence of invasive S. invicta may compromise the utility of cover boards and other techniques commonly used in herpetological studies in the Southeast.     

Rodents balancing a variety of risks: invasive fire ants and indirect and direct indicators of predation risk

We used foraging trays to compare how oldfield mice, Peromyscus polionotus, altered foraging in response to the presence of fire ants, Solenopsis invicta, and in the presence of direct (predator urine) and indirect (sheltered or exposed microhabitat, moonlight, and precipitation) indicators of predation risk. Foraging reductions elicited by S. invicta were greater than reductions in response to well-documented indicators of risk (i.e., moonlit nights) and the presence of predator urine. The presence of S. invicta always led to reduced foraging, but the overall impact of S. invicta was dependent upon microhabitat and precipitation. When S. invicta was not present, foraging was greater in sheltered microhabitats compared to exposed microhabitats. S. invicta made sheltered microhabitats equivalent to more risky exposed microhabitats, and this effect was especially pronounced on nights without precipitation. The effect of S. invicta suggests that interactions with S. invicta may entail a potentially heavy cost or that presence of S. invicta may represent a more reliable indicator of imminent competition or predation compared to indirect cues of risk and predator urine. The presence of S. invicta led to reduced foraging under situations when foraging activity would otherwise be greatest (i.e., under vegetative cover), potentially reducing habitat quality for P. polionotus and the distribution of seeds consumed by rodents.     

Evaluating biological control of fire ants using phorid flies: effects on competitive interactions

The effects of the parasitic phorid fly, Pseudacteon tricuspis Borgmeier, on the competitive interactions between the red imported fire ant, Solenopsis invicta Buren, and a native North American ant, Forelius pruinosus (Roger), were investigated in the laboratory. P. tricuspis is a highly host-specific endoparasitoid of S. invicta workers that is currently being reared and released as a biological control agent of S. invicta in the US. We tested the effect of P. tricuspis on the colony growth rate of S. invicta when S. invicta was forced to compete with F. pruinosus for a protein resource (freeze-killed crickets) in laboratory competition arenas. In addition to colony growth rate, we quantified the effect of the phorid flies on the foraging rate of S. invicta. Though S. invicta significantly reduced its foraging rate in the presence of the phorid flies, we did not detect an effect of the flies on colony growth rate. Possible explanations for these results include behavioral compensation by S. invicta for the presence of the flies. We present these laboratory results in light of a literature search indicating that laboratory tests of biological control agent efficacy are good predictors of field efficacy. We conclude that P. tricuspis alone is unlikely to suppress S. invicta populations in the field by reducing their competitive ability.     

昆明红火蚁种群发生特征

【目的】2013年10月云南省元谋县首次发现红火蚁。掌握红火蚁蚁巢各品级发生动态,能为当地红火蚁的防控提供技术支撑。【方法】2015年1—12月,在昆明宜良县对红火蚁蚁巢取样、分离,红火蚁取样、称重,统计红火蚁各品级的头数。【结果】地上蚁巢红火蚁蚁群数量发生高峰期在8—9月,其次是3—4月。蚁后数量比例高峰在3—4月;有翅雌蚁比例高峰在4月,其次是7月;有翅雄蚁比例高峰的在5月,其次是9月;生殖蚁幼虫和蛹比例高峰的3、4和12月。地上蚁巢工蚁、兵蚁、职能蚁幼虫和蛹数量发生的高峰期在8—9月,发生小高峰期在4月。【结论】昆明红火蚁蚁群数量动态有2个峰值,第一个峰值为8—9月,以职能蚁防治为主;第二个蜂值3—4月,以生殖蚁和职能蚁防治为主。该结果为昆明红火蚁防控技术提供了数据支撑。     

Post-Release Host-Specificity Testing of Pseudacteon tricuspis, a Phorid Parasitoid of Solenopsis Invicta Fire Ants

Inherent in any biological control program is the risk of nontarget effects. Pseudacteon tricuspisBorgmeier, a parasitoid phorid fly, has been introduced to the United States from South America as a potential biocontrol agent of the red imported fire ant, Solenopsis invictaBuren. We conducted tests of host specificity on introduced populations of P. tricuspis, which are attracted to alarm pheromones released by their hosts during events such as mound disturbances and interspecific interactions. We monitored disturbed mounds of S. invicta and its close congener, S. geminata(F.), during the expansion of P. tricuspis across north Florida and after populations had been established for ~3 years. We also tested host acceptance in established populations of P. tricuspis by offering trays containing S. invicta, S. geminata, and 14 additional ant species representing 12 different non-Solenopsis genera. Although P. tricuspiswas commonly observed to hover over and attempt to oviposit on S. invicta, we never observed any parasitization attempts on any other ant species. As predicted by laboratory tests, released populations of P. tricuspis appear to be highly host specific and pose no obvious threat to nontarget species.     

Apparent facilitation of an invasive mealybug by an invasive ant

Summary In the southeast United States, the invasive ant Solenopsis invicta is known to derive important carbohydrate (honeydew) resources from mealybugs utilizing grasses. Most important appears to be an invasive mealybug, Antonina graminis. We studied whether this mealybug and a similar native species also benefit from association with S. invicta. We found that mealybug occurrence increases significantly with increasing proximity to S. invicta mounds, suggesting that mealybugs benefit as well. Mutual benefits derived by S. invicta and A. graminis are consistent with a hypothesis proposing that associations among invasive species can be important in their success at introduced locations.     

A new baited trap for monitoring <Emphasis Type="Italic">Solenopsis invicta</Emphasis> (Formicidae: Hymenoptera) in Taiwan

This study investigated the efficacy of the newly designed hotdog-baited trap (B-trap) to detect red imported fire ants (RIFA), Solenopsis invicta Buren, under field conditions in Taiwan. Among the seven different food lures examined using RIFA, hotdogs were the most preferred by the ants, followed by shrimp crackers and potato chips. Hotdogs were therefore used in the B-trap, and a comparison was made with the traditional pitfall trap (A-trap) to determine their efficacy in trapping RIFA. Field data revealed that the B-trap was more efficient than the A-trap based on its ability to trap more RIFA under field conditions and its ease of use. Thus, it was concluded that the B-trap is an efficient trap for long-term RIFA monitoring in Taiwan.     

海南省降香黄檀害虫种类、分布及危害症状调查

【背景】降香黄檀被确定为海南省省树后,种植面积迅速增大,但对于其病虫害的监测与防控方面的研究较少。【方法】采用人工采集结合灯光诱集的方法,调查降香黄檀种植区的害虫种类,同时对其危害症状进行了详细描述。【结果】海南降香黄檀害虫共计19种,确定了其中18种的学名,并掌握了各害虫的分类学地位、危害部位及症状。害虫在降香黄檀植株各个组织部位均有分布,其中以叶部的分布数量较大,茎干次之。苗期以食叶性害虫居多;5年生以内的植株上蛀干害虫数量显著增多;老龄植株上的茎干害虫较少。【结论与意义】海南省降香黄檀各生育期均有害虫危害,日后仍需加强对其害虫监测与防控技术的研究。     

云南扶桑绵粉蚧的发生及防治

扶桑绵粉蚧是一种全球恶性入侵害虫,2008年传入我国,目前已有13个省区报道其为害,2009年在云南省被发现,截至2013年3月,云南省共8个州(市) 10个县(市)已有分布。扶桑绵粉蚧寄主范围广,危害性大,适应性强。同时,云南省花卉、蔬菜调运及进出口贸易频繁,加之气候类型丰富、水热条件优越、自然地理环境复杂多样、动植物资源丰富等优势,有利于扶桑绵粉蚧的入侵、定殖与扩散,易造成较大的经济损失。目前,关于云南省扶桑绵粉蚧的研究仍然缺乏,现就扶桑绵粉蚧在云南的发生现状、潜在风险和防治措施等方面进行概述,以期为该虫的有效防范提供参考。     

The urban fire ant paradox: native fire ants persist in an urban refuge while invasive fire ants dominate natural habitats

In contrast to the widespread extirpation of native fire ants (Solenopsis geminata) across southern US following the invasion by imported red fire ants (S. invicta), some residential areas of Austin form unexpected refuges for native fire ants. Ironically, these urban environments provide refuges for the native fire ants while adjacent natural habitats have been overrun by invasive fire ants. Resistance to invasive fire ants in these urban areas occurs mainly in older residential properties constructed prior to the S. invicta invasion, while more recent construction has allowed establishment by S. invicta. The invasive ability of S. invicta is often attributed to escape from parasitoids and efficient dispersal of polygyne multiple queen colonies. Here we also show the importance of landscape parameters in the invasion process, where low levels of disturbance and continuous plant cover in older residential areas form possible barriers to colonization. Dense leaf cover (high NDVI) was also found to be associated with native ant refuges. Long term residential land ownership may have resulted in lower recent disturbance levels and increased plant cover that support refuges of native fire ants.     

严防外来有害生物褐纹甘蔗象入侵海南

【背景】褐纹甘蔗象原产于菲律宾,严重危害椰子等棕榈科植物和甘蔗,目前该虫已传入我国台湾、广东、广西和云南,尚未在海南省发生。【方法】为尽早预防该虫传入,本文简要描述了褐纹甘蔗象的生物生态学特性,并运用有害生物危险性分析(PRA)方法,从国内分布情况、潜在的经济危害性、受害寄主的经济重要性、传播扩散的可能性和危险性管理难度等方面对该虫入侵海南的可能性进行了定性和定量分析。【结果】褐纹甘蔗象在海南省的风险评估值R=2.08,属于高风险的林业有害生物,建议将其列入海南省林业检疫性有害生物名单;同时提出了该虫的综合防治措施和建议。【结论与意义】本研究可为尽早制定褐纹甘蔗象防范措施提供参考。     

Myrmica specioides Bondroit: a new invasive ant species in the USA?

Ants are among the most successful invasive species. The establishment of the infamous red imported fire ant Solenopsis invicta (Fabricius) has caused a considerable amount of damage to both the economy and the native ecosystem of the Southern United States. We report the first record of a newly introduced ant species, Myrmica specioides Bondroit, to the state of Washington. It possesses the characteristics of a potential pest ant: high aggressiveness, polygyny, and the tendency to reach high local abundances. This early record might facilitate the control of introduced populations before they can develop into a genuine nuisance.     

Ontogeny of the Defensive Stinging Behavior of the Fire Ant, Solenopsis invicta

The fire ant, Solenopsis invicta, appears to deviate from the usual age-related pattern of defensive behavior seen in other social insects; instead of older workers being more defensive than younger ones, they are less so. Here I test this pattern by quantifying changes in the defensive stinging behavior of S. invicta workers of known age. I found defensiveness, measured as both the number of stings delivered and the amount of venom delivered per sting (venom dose), to increase with age initially but then decline after a mid-age peak. This hump-shaped ontogeny may be the result of S. invicta's foraging strategy, which effectively shifts the responsibility of nest defense to workers younger than foraging age. It is S. invicta's mid-aged workers that are the most defensive, probably because they are both physiologically and spatially the most suitable nest defenders.     

Culture-independent identification of gut bacteria in fourth-instar red imported fire ant, Solenopsis invicta Buren, larvae

Red imported fire ants (RIFA), Solenopsis invicta Buren, are medical, urban, and agricultural pests from South America. They are successful invaders due to their preference for disturbed habitats, high reproductive rates, and the ability to feed on a wide variety of food items (omnivorous). Fourth-instar larvae are used by the colony to digest solid food and then regurgitate it for consumption by workers and queens. Larvae are an ideal source of investigations of endosymbiotic bacteria possibly involved in nutrient distributions. Our study utilized 16S rDNA sequencing to describe the composition of the bacterial community in fourth-instar ant larvae in order to identify possible endosymbiotic bacteria present therein. The 16S rRNA gene was directly amplified from mixed-population DNA of whole fire ant larval guts and cloned into Escherichia coli. Bacterial communities from three geographically separated RIFA colonies were examined. Sequenced bacterial clones from guts were determined to be predominantly from the phylum Proteobacteria and the family Enterobacteriaceae. Our results did not detect the presence of endosymbiotic bacteria in the guts of RIFA larvae among the colonies. In addition, minimal species overlap was found when bacterial inventories were compared among colonies. Thus, bacteria coadapted with red imported fire ant larvae were not detected. Identified bacteria were not closely affiliated with endosymbiotic bacteria common in other insect species. Bacteria communities appeared to be unique to each geographical location and were determined by the foods consumed by the ants.     

Antipredatory Activity of the Weevil Oxyops vitiosa: A Biological Control Agent of Melaleuca quinquenervia

The larvae of the leaf-feeding weevil Oxyops vitiosa, a biological control agent of Melaleuca quinquenervia, are covered with a viscous orange coating that is thought to protect against generalist predators. This coating is gradually lost as the larvae drop to the ground and pupate in subterranean pupal cells. To test the antipredator activity of this species, four immature life stages (early instars, late instars, prepupae, pupae) were exposed to a common generalist predator, the red imported fire ant Solenopsis invicta. Choice tests were conducted by placing an O. vitiosa individual and a control larva of the weevil Neochetina eichhorniae into an arena containing a S. invicta colony and observing subsequent ant behaviors. S. invicta workers contacted O. vitiosa early instars, late instars, and prepupae less frequently than control N. eichhorniae larvae, and upon contact S. invicta was less likely to behave aggressively toward these O. vitiosa life stages than toward N. eichhorniae larvae. However, S. invicta contacted, attacked, and consumed naked (nonencased) O. vitiosa pupae and N. eichhorniae larvae with equal frequency. Encased O. vitiosa pupae buried in sand were not attacked compared to susceptible encased pupae on the sand surface. By shifting from a chemical defense during the larval stages to a physical defense during the pupal stage, O. vitiosa reduces the risk of attack by this generalist predator.     

海南发现椰子织蛾的重要天敌褐带卷蛾茧蜂

椰子织蛾是棕榈植物的重要入侵害虫,在印度和斯里兰卡严重危害椰子树。2013年在海南省万宁市首次发现椰子织蛾。目前,该虫已在海南多个市县及广东和广西危害,对我国棕榈科植物的安全生产构成严重威胁。2014年11月,作者等人在万宁兴隆和三亚海棠湾镇调查椰子织蛾危害时,发现其重要天敌昆虫——褐带卷蛾茧蜂。为了进一步了解褐带卷蛾茧蜂,本文对其形态特征、分布、寄主和生物学习性进行了报道,以便更好地用于椰子织蛾的生物防治。     

江苏省花椒属(芸香科)植物地理分布新记录

报道江苏省花椒属地理分布新记录植物1种——椿叶花椒(Zanthoxylum ailanthoides Sieb.et Zucc.),并对该省花椒属植物进行了补充记述。椿叶花椒分布于中国东南部(福建、浙江、江西、广东、广西、贵州、四川、云南、台湾)至东亚和东南亚的热带与亚热带地区,在江苏为新记录,且是该种分布的最北界。凭证标本存放于南京师范大学生命科学学院生物标本馆(NJNUH)。