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.     

Chemical tools to distinguish the fire ant species Solenopsis invicta and S. saevissima (Formicidae: Myrmicinae) in Southeast Brazil

Morphologically similar fire ants Solenopsis invicta and Solenopsis saevissima are broadly sympatric in southeastern Brazil. Chemistry from venom (2,6-dialkyl piperidine alkaloids) and cuticular hydrocarbons have been reported as potentially important tools for differentiating Solenopsis species. We have analysed two chemical classes in widely separated populations of S. invicta and S. saevissima and find that both piperidine alkaloids and cuticular hydrocarbons separate the two species. Piperidine alkaloids clustered S. invicta but not S. saevissima. Cuticular hydrocarbons strongly clustered both S. invicta and S. saevissima. One population morphologically identified as S. invicta presented piperidine alkaloids and cuticular hydrocarbons markedly different from either species. The distinctive piperidine alkaloid differences among populations of S. saevissima and the marked difference in piperidine alkaloid and hydrocarbon profiles of the anomalous population of S. invicta suggest undescribed species fire ant in southeastern Brazil.     

Effects Of Tending By Solenopsis Invicta (Hymenoptera: Formicidae) On The Sugar Composition And Concentration In The Honeydew Of An Invasive Mealybug,Phenacoccus Solenopsis (Hemiptera: Pseudococcidae)

Mutualistic interactions between ants and hemipterans are mediated by the honeydew produced by the hemipterans. Previous works have demonstrated that the invasive mealybug Phenacoccus solenopsis produces abundant honeydew and attracts a large number of workers of the fire ant Solenopsis invicta. Mealybugs exhibit higher fecundity when tended by fire ants. The honeydew produced by P. solenopsis plays an important role in interactions between these two species. However, relatively few studies have focused on whether there is a cost to P. solenopsis mealybugs of being tended by S. invicta through changes in their excretion behavior and the quantity of honeydew produced. Our results indicated that the honeydew of P. solenopsis contains xylose, fructose, sucrose, trehalose, melezitose, and raffinose. The sugar concentration in the mealybug honeydew changed in an ant‐tended treatment. When tended by fire ants, the mealybugs generated honeydew with a significantly decreased xylose concentration. In contrast, the droplets showed a considerable increase in the melezitose concentration. P. solenopsis excreted honeydew more frequently when tended by S. invicta, but the weights of the droplets excreted by the ant‐tended mealybugs were significantly lower. In addition, S. invicta exhibited a significant preference for different sugars. Melezitose was visited more intensively than the other sugars in two choice tests. These results may suggest that, to attract more tending ants, mealybugs adjust their carbohydrate metabolism.     

The nutrient capital of indigenous Sorghum species and other understorey components of Savannas in north-western Australia

Indigenous Sorghum species dominate the understorey of the savannas of tropical northwestern Australia. The nutrient capital of these grasses was investigated and the consequences for nutrient cycling, the effects of fire, and herbivory were discussed. The macronutrient concentrations in two annual species, S. intrans and S. stipoideum indicated that their growth was nutrient limited. The breakdown of litter may provide up to one quarter of the N yield of S. intrans, hence losses of N due to dry season fires, which consume this litter, may reduce grass growth. However, this effect was not apparent after one fire. From the first sampling, approximately 60 days after germination, until maturity, the herbage of S. intrans and S. stipoideum contained insufficient N and P to maintain the liveweight of cattle. Translocation to the inflorescence during seed set left the herbage grossly deficient for livestock maintenance during the dry season. The relative lack of large native herbivores is consistent with this poor herbage quality. Nutrient concentrations in the seeds of nine Sorghum species (including two perennials) were measured. The concentrations were relatively high, which accounts for the importance of the seeds of the indigenous Sorghum species for granivorous rodents, birds, and ants. Macro-nutrient concentrations were similar in both annual and perennial species.     

COMPARATIVE BIOCHEMICAL GENETICS OF THREE FIRE ANT SPECIES IN NORTH AMERICA,WITH SPECIAL REFERENCE TO THE TWO SOCIAL FORMS OF SOLENOPSIS INVICTA (HYMENOPTERA: FORMICIDAE)

An electrophoretic study of the genetics of three fire ant species in North America was undertaken with the primary objective of further clarifying the genetic relationship between two social forms of Solenopsis invicta. Such social forms are common in many groups of ants and may, in some cases, represent significant intermediate stages in the speciation process. The monogyne and polygyne forms of S. invicta, while differing in a number of important biological traits, are genetically indistinguishable, in contrast to the substantial genetic differentiation observed between S. invicta and a second, closely related, introduced species, S. richteri. The native fire ant, S. geminata, is genetically the most distinct of the three species studied, in accord with its taxonomic placement in a different species complex. Hypotheses concerning the derivation of the polygyne form of S. invicta from the monogyne form which invoke their long-term reproductive isolation in South America and separate introductions to North America appear unfounded. Although S. invicta and S. richteri are known to hybridize in North America, our study provided no evidence of gene introgression between S. invicta and the native species, S. geminata, in areas where our samples were collected. Analyses of population structure in S. invicta failed to reveal significant differentiation of populations or local inbreeding. Levels of genetic diversity in the three species studied, although not significantly different, were in the order predicted from knowledge of the population biology and recent history of the taxa, with S. richteri exhibiting the least diversity, S. geminata the greatest, and S. invicta having an intermediate level.     

Reproduction by virgin queen fire ants in queenless colonies: Comparative study of three taxa (Solenopsis richteri,hybridS. invicta/richteri,S. geminata) (Hymenoptera: Formicidae)

Summary In the fire ant,Solenopsis invicta, some winged virgin queens are known to shed their wings (dealate) upon removal of the mated mother queen. These virgin queens then develop their ovaries and begin to lay eggs, thereby foregoing the option of leaving on mating flights and attempting to found their own colonies. Such a response of virgin queens to queenlessness has not been reported for other ants. In order to determine if virgin queens of some other fire ants (subgenusSolenopsis) would respond in the same way, experiments were conducted onS. richteri, hybridS. invicta/richteri andS. geminata, a member of a species complex different from that of the other taxa. Just as inS. invicta, virgin queens ofS. richteri and the hybrid dealated and began to lay eggs within days of the removal of the queen. In addition, workers executed many of the reproductively active virgin queens, a phenomenon also found inS. invicta. In contrast, virgin queens ofS. geminata did not dealate or quickly begin to lay eggs upon separation from the queen. Reasons for the variability in the response of virgin queens of the different species may be 1) higher probability of reproductive success for unmated dealated queens compared to normal claustral founding inS. invicta andS. richteri linked to relatively frequent loss of the mother queen; or 2) phylogenetic constraint.     

Disruption of parasitism of the California red scale (Homoptera: Diaspididae) by three ant species (Hymenoptera: Formicidae)

The relative influence of the southern fire ant, Solenopsis xyloni McCook, Argentine ant, Linepithema humile (Mayr), and native gray ant, Formica aerata (Francoeur), on parasitism of California red scale, Aonidiella aurantii Maskell, was studied in the laboratory for two parasitoids, Comperiella bifasciata Howard and Aphytis melinus DeBach. All three ant species reduced percentage parasitism by C. bifasciata and both percentage parasitism and host mutilation by A. melinus. Southern fire ant was the least disruptive and native gray ant the most disruptive. Southern fire ant removed 12% of scale from the lemons, presumably to feed on them, while the other ant species did not exhibit significant removal of scale compared to the controls. Percentage parasitism of California red scale exhibited by C. bifasciata was more than 2-fold the level exhibited by A. melinus. Percentage mutilation of California red scale, including probing and host feeding, was nearly 5-fold higher for A. melinus than C. bifasciata. Because A. melinus required a longer total host examination + oviposition period in the absence of ants than C. bifasciata and because oviposition occurs as the last act in a sequence of behaviors, disruption by the ants had a more significant negative effect on oviposition by A. melinus.     

Reaction of Ants to, and Feeding Biology of, a Congeneric Myrmecophilous and Non-myrmecophilous Ladybird

Coccinella magnifica Redtenbacher lives only in close contact with species of the Formica rufa group. Laboratory experiments were set up to determine how this species may be adapted to living with ants by comparing its behaviour with that of the closely related Coccinella septempunctata L. Eggs and larvae of C. magnifica placed on the foraging trails of ants were bitten significantly less often by the ants than those of C. septempunctata. However, the ants responded similarly to the adults of both species. For these two species, the presence of ants resulted in a significant decrease in predation efficiency. However, C. magnifica was more efficient at catching aphids in the presence of ants than C. septempunctata. The behaviour of this myrmecophilous species is discussed by taking into account that it is a generalist in terms of prey specificity.     

A Bryophyte flora of Cornwall. II. Sphagna

Abstract

The taxonomy of Anomobryum julaceum and allied species with axillary bulbils in Europe and Asia is reviewed. A. concinnatum is regarded as a distinct species, occurring in W. and C. Europe, SW., N. and C. Asia and N. America. A. bavaricum has often been confused with A. concinnatum, but differs in its more numerous, small, reddish bulbils and in leaf shape; it is known only from the European Alps. The Asian A. nitidum also has numerous small reddish bulbils but it differs from A. bavaricum in leaf shape and bulbil form. A lectotype is designated for A. nitidum, of which A. gemmigerum and other nominal taxa are regarded as synonyms. Information is presented on geographical ranges and habitats of the four valid species.     

Immediate impacts of invasion by Wasmannia auropunctata (Hymenoptera: Formicidae) on native litter ant fauna in a New Caledonian rainforest

Abstract For the last 30 years, Wasmannia auropunctata (the little fire ant) has spread throughout the Pacific and represents a severe threat to fragile island habitats. This invader has often been described as a disturbance specialist. Here we present data on its spread in a dense native rainforest in New Caledonia. We monitored by pitfall trapping the litter ant fauna along an invasive gradient from the edge to the inner forest in July 1999 and March 2000. When W. auropunctata was present, the abundance and richness of native ants drops dramatically. In invaded plots, W. auropunctata represented more than 92% of all trapped ant fauna. Among the 23 native species described, only four cryptic species survived. Wasmannia auropunctata appears to be a highly competitive ant that dominates the litter by eliminating native ants. Mechanisms involved in this invasive success may include predation as well as competitive interactions (exploitation and interference). The invasive success of W. auropunctata is similar to that of other tramp ants and reinforces the idea of common evolutionary traits leading to higher competitiveness in a new environment.     

Ecological dominance of the red imported fire ant, <Emphasis Type="Italic">Solenopsis invicta</Emphasis>, in its native range

Despite the widespread impacts invasive species can have in introduced populations, little is known about competitive mechanisms and dominance hierarchies between invaders and similar taxa in their native range. This study examines interactions between the red imported fire ant, Solenopsis invicta, and other above-ground foraging ants in two habitats in northeastern Argentina. A combination of pitfall traps and baits was used to characterize the ant communities, their dominance relationships, and to evaluate the effect of phorid flies on the interactions. Twenty-eight ant species coexisted with S. invicta in a gallery forest gap, whereas only ten coexisted with S. invicta in a xerophytic forest grassland. S. invicta was the most numerically dominant species in the richest and complex habitat (gallery forest); however it performed better as discoverer and dominator in the simpler habitat. S. invicta was active during day and night. In spite of its poor capacity to discover resources, S. invicta showed the highest ecological dominance and the second-best behavioral dominance after Camponotus blandus. S. invicta won 78% of the interactions with other ants, mostly against its most frequent competitor, Pheidole cf. obscurithorax, dominating baits via mass recruitment and chemical aggression. P. cf. obscurithorax was the best food discoverer. S. invicta won 80% of the scarce interactions with Linepithema humile. Crematogaster quadriformis was one of the fastest foragers and the only ant that won an equal number of contests against S. invicta. The low presence of phorid flies affected the foraging rate of S. invicta, but not the outcome of interspecific interactions. This study revealed that the red imported fire ant ecologically dominated other terrestrial ants in its native range; however, other species were able to be numerically dominant or co-dominant in its presence.     

Interspecific displacement mechanisms by the invasive little fire ant <Emphasis Type="Italic">Wasmannia auropunctata</Emphasis>

Competition between invasive species and native ones in the new environment was found to be significant and to affect both animal and plant species. Invasive ants are notorious for displacing local ant species through competition. Competitive displacement of native species can occur through interference and or resource competition. However, for invasive ants, little is known about the relative importance of competitive displacement. We studied competitive interactions of the little fire ant, Wasmannia auropunctata, one of the most destructive invasive ant species, with two other ant species, Monomorium subopacum and Pheidole teneriffana. We compared the species’ foraging behavior and studied their aggressive interactions around food baits for the short (2 h) and long (21 days) term in the laboratory. Surprisingly we found that in short term experiments W. auropunctata had the poorest foraging abilities of the three species studied: it took the workers the longest to locate the bait and retrieve it; in addition they retrieved the lowest amount of food. When both W. auropunctata and M. subopacum were foraging the same bait, in the short term competition experiment, W. auropunctata workers did not defend the bait, and ceased foraging when encountered with competition. The long-term experiments revealed that W. auropunctata had the advantage in aggressive interactions over time; they eliminated seven of nine M. subopacum’s nests while consuming some of the workers and brood. According to our laboratory studies, W. auropunctata cannot be considered an extirpator species, unless it has a substantial numerical advantage, in contrast with previous assumptions. Otherwise it may behave as an insinuator species, i.e. the workers do not initiate aggression and by staying undetected they can continue foraging adjacent to dominant species.     

A multigene molecular assessment of cryptic biodiversity in the iconic freshwater blackfishes (Teleostei: Percichthyidae: Gadopsis) of south‐eastern Australia

Freshwater biodiversity is under ever increasing threat from human activities, and its conservation and management require a sound knowledge of species‐level taxonomy. Cryptic biodiversity is a common feature for aquatic systems, particularly in Australia, where recent genetic assessments suggest that the actual number of freshwater fish species may be considerably higher than currently listed. The freshwater blackfishes (genus Gadopsis) are an iconic group in south‐eastern Australia and, in combination with their broad, naturally divided distribution and biological attributes that might limit dispersal, as well as ongoing taxonomic uncertainty, they comprise an ideal study group for assessing cryptic biodiversity. We used a multigene molecular assessment including both nuclear (51 allozyme loci; two S7 introns) and matrilineal markers (cytb) to assess species boundaries and broad genetic substructure within freshwater blackfishes. Range‐wide examination demonstrates the presence of at least six candidate species across two nominal taxa, Gadopsis marmoratus and Gadopsis bispinosus. Phylogeographical patterns often aligned to purported biogeographical provinces but occasionally reflected more restricted and unexpected relationships. We highlight key issues with taxonomy, conservation, and management for a species group in a highly modified region. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 521–540.     

Molecular phylogeny of fire ants of the Solenopsis saevissima species-group based on mtDNA sequences

The systematics of South American fire ants (Solenopsis saevissima species-group) has been plagued by difficulties in recognizing species and their relationships on the basis of morphological characters. We surveyed mtDNA sequences from 623 individuals representing 13 described and undescribed species within the species-group and 18 individuals representing other major Solenopsis lineages to generate a phylogeny of the mitochondrial genome. Our analyses support the monophyly of the S. saevissima species-group, consistent with a single Neotropical origin and radiation of this important group of ants, as well as the monophyly of the socially polymorphic species within the group, consistent with a single origin of polygyny (multiple queens per colony) as a derived form of social organization. The mtDNA sequences of the inquiline social parasite S. daguerrei form a clade that appears to be distantly related to sequences from the several host species, consistent with the view that advanced social parasitism did not evolve via sympatric speciation of intraspecific parasites. An important general finding is that species-level polyphyly of the mtDNA appears to be the rule in this group of ants. The existence of multiple divergent mtDNA lineages within several nominal species (including the pest S. invicta) suggests that the pattern of widespread polyphyly often stems from morphological delimitation that overcircumscribes species. However, in two cases the mtDNA polyphyly likely results from recent interspecific hybridization. While resolving species boundaries and relationships is important for understanding general patterns of diversification of South American fire ants, these issues are of added importance because invasive fire ants are emerging as global pests and becoming important model organisms for evolutionary research.     

Systematics of spiny‐backed treefrogs (Hylidae: Osteocephalus): an Amazonian puzzle

Spiny‐backed tree frogs of the genus Osteocephalus are conspicuous components of the tropical wet forests of the Amazon and the Guiana Shield. Here, we revise the phylogenetic relationships of Osteocephalus and its sister group Tepuihyla, using up to 6134 bp of DNA sequences of nine mitochondrial and one nuclear gene for 338 specimens from eight countries and 218 localities, representing 89% of the 28 currently recognized nominal species. Our phylogenetic analyses reveal (i) the paraphyly of Osteocephalus with respect to Tepuihyla, (ii) the placement of ‘Hyla’ warreni as sister to Tepuihyla, (iii) the non‐monophyly of several currently recognized species within Osteocephalus and (iv) the presence of low (<1%) and overlapping genetic distances among phenotypically well‐characterized nominal species (e.g. O. taurinus and O. oophagus) for the 16S gene fragment used in amphibian DNA barcoding. We propose a new taxonomy, securing the monophyly of Osteocephalus and Tepuihyla by rearranging and redefining the content of both genera and also erect a new genus for the sister group of Osteocephalus. The colouration of newly metamorphosed individuals is proposed as a morphological synapomorphy for Osteocephalus. We recognize and define five monophyletic species groups within Osteocephalus, synonymize three species of Osteocephalus (O. germani, O. phasmatus and O. vilmae) and three species of Tepuihyla (T. celsae, T. galani and T. talbergae) and reallocate three species (Hyla helenae to Osteocephalus, O. exophthalmus to Tepuihyla and O. pearsoni to Dryaderces gen. n.). Furthermore, we flag nine putative new species (an increase to 138% of the current diversity). We conclude that species numbers are largely underestimated, with most hidden diversity centred on widespread and polymorphic nominal species. The evolutionary origin of breeding strategies within Osteocephalus is discussed in the light of this new phylogenetic hypothesis, and a novel type of amplexus (gular amplexus) is described.     

Patterns of abundance of fire ants and native ants in a native ecosystem

Abstract 1. This correlational study examines the relationship between the red imported fire ant (Solenopsis invicta) and native ants in a longleaf pine savanna. Fire ants are frequently associated with a decline in native ants throughout the invaded range, but fire ant invasion is often coupled with habitat disturbance. Invasion of fire ants into the longleaf pine savanna provides an opportunity to examine the structure of the ant community in the absence of habitat disturbance. 2. Pitfall trapping was conducted within the longleaf pine savanna as well as across a naturally occurring soil moisture gradient, in plots that had been artificially watered. 3. Species richness did not vary as a function of fire ant density. There was an inverse relationship between native ant density and fire ant density, but this abundance pattern does not necessarily imply a causal link between fire ant invasion and native ant decline. For individual species, fire ant densities were negatively correlated with the densities of only two native ant species, including Solenopsis carolinensis, a native species that potentially limits the invasion of fire ants. Additionally, fire ants and native ants respond differently to soil moisture, with native ants favouring drier conditions than fire ants. 4. The possible exclusion of fire ants by some native ants, as well as differences in habitat preferences, provide alternative explanations for the frequently observed negative correlation between fire ants and native ants.     

Molecular phylogeny of the South American land slug Phyllocaulis (Mollusca,Soleolifera, Veronicellidae)

Gomes, S. R., Britto da Silva, F., Mendes, I. L. V., Thomé, J. W. & Bonatto, S. L. (2009). Molecular phylogeny of the South American land slug Phyllocaulis (Mollusca, Soleolifera, Veronicellidae). —Zoologica Scripta, 39, 177–186. Our main objectives were investigate the phylogenetic relationships between the species of the land slug Phyllocaulis and the monophyly of the genus based on mitochondrial (16S and COI) and nuclear (ITS2) DNA sequences from multiple individuals from each species. Evolutionary trees were constructed using Bayesian inference, maximum likelihood, maximum parsimony and neighbor‐joining methods. All species accepted in the current taxonomy based on penial characteristics and radular measurements were reciprocally monophyletic. Five species out of six formed a clade with the following highly supported relationship: Phyllocaulis gayi, Phyllocaulis soleiformis, Phyllocaulis renschi, Phyllocaulis variegatus, Phyllocaulis boraceiensis. The position of Vaginulus taunaisii changed according to the analysis, appearing as sister‐group of Phyllocaulis or as sister‐group of Phyllocaulis tuberculosus. Divergence times estimated from the 16S tree indicated that the extant species of Phyllocaulis shared a common ancestor around 1.3 Ma and that most species originated between 0.8 and 0.6 Ma.     

Ant effects on three-trophic level interactions: plant, galls, and parasitoids

1. Ants have evolved mutualistic relationships with a diverse array of plant and animal species. Usually, the predatory/aggressive behaviour of ants near food sources can limit herbivore damage. 2. Galls of Disholcaspis edura on Quercus turbinella produce a secretion that is harvested by three species of ants (Formica neorufibarbis, Liometopium apiculatum, and Monomorium cyaneum) in the chaparral vegetation of Arizona, U.S.A. The study reported here provides evidence of a mutualistic relationship between these species of ants and the gall-forming wasp Disholcaspis edura. 3. An ant exclusion experiment showed that when ants tended galls, the rate of parasitism by Platygaster sp. on Disholcaspis edura was nearly halved in comparison to a treatment in which ants were excluded. 4. In the presence of ants, galls with the largest diameter suffered a lower mortality rate due to parasitoid attack than when ants were excluded. Thus, ant presence reduced the selective pressure imposed by Platygaster sp. on the galls with larger diameter.     

Imported crazy ant displaces imported fire ant, reduces and homogenizes grassland ant and arthropod assemblages

A recently introduced, ecologically dominant, exotic ant species, Nylanderia fulva, is invading the Southeastern United States and Texas. We evaluate how this invader impacts diversity and abundance of co-occurring ants and other arthropods in two grasslands. N. fulva rapidly attains densities up to 2 orders of magnitude greater than the combined abundance of all other ants. Overall ant biomass increases in invaded habitat, indicating that N. fulva exploits resources not fully utilized by the local ant assemblage. At high density, as N. fulva spreads, it eliminates the current ecologically dominant invasive ant, red imported fire ants (Solenopsis invicta). Compared to imported fire ant dominated habitat, N. fulva invasion zones have lower non-ant arthropod species richness and abundance with impacts differing by trophic category. Further, N. fulva reduces abundance and species richness of the remainder of the ant assemblage and does so in a non-random manner: impacting species with small sized workers much less than species with larger workers. In these and other ant assemblages with a large exotic component, the exotics tend to be small bodied species. As a result, N. fulva almost completely eliminates regionally distributed species, but leaves globally distributed species largely unaffected, thereby systematically favoring introduced over native diversity. S. invicta impacts wildlife and arthropod assemblage structure and is nearly ubiquitous in non-forested habitats of the Southeastern United States and Texas. Its displacement by N. fulva has critical implications for the natural systems of this region.     

Pseudacteon decapitating flies (Diptera: Phoridae): Are they potential vectors of the fire ant pathogens Kneallhazia (=Thelohania) solenopsae (Microsporidia: Thelohaniidae) and Vairimorpha invictae (Microsporidia: Burenellidae)?

Fire ant decapitating flies in the genus Pseudacteon were tested for their potential as hosts or vectors of two microsporidian pathogens of the red imported fire ant, Solenopsis invicta. Decapitating flies that attacked or were reared from S. invicta workers infected by Kneallhazia (=Thelohania) solenopsae or Vairimorpha invictae were tested for either pathogen by polymerase chain reaction (PCR) tests or visual examination for spores using phase microscopy. Three species of fire ant decapitating flies acquired the pathogen, Kneallhazia solenopsae. K. solenopsae was detected in 58% of pooled samples of Pseudacteon obtusus flies and 44% of pooled samples of Pseudacteon cultellatus that developed in K. solenopsae-infected fire ant workers. K. solenopsae was also found in 17% of pooled samples of field-collected Pseudacteon curvatus. In contrast, the microsporidium V. invictae was not detected in P. obtusus reared from V. invictae-infected S. invicta workers. Neither K. solenopsae nor V. invictae were detected in any of the hovering or ovipositing flies in the laboratory exposures, indicating no mechanical acquisition of the microsporidia occurred during oviposition activity. Greater than 92% of the P. obtusus that developed in K. solenopsae-infected ants survived and emerged as adults, thus indicating no detrimental effects of the microsporidium on pupal development and emergence. These results indicate that Pseudacteon decapitating flies may be able to vector K. solenopsae but not V. invictae among fire ants. Further tests are planned to determine if flies containing K. solenopsae are capable of transferring this pathogen either during oviposition or by being consumed by fire ant larvae.