The red imported fire ant (RIFA) was introduced to the United States from South America over 75 years ago, and has become a pest in wildlife settings. Hydramethylnon fire ant bait has been the industry standard for controlling the red imported fire ant. It can be compared to novel baits, and used to evaluate different aerial application techniques, such as the "skip swath" method. Two baits, hydramethylnon and metaflumizone, and a skipped-swath method were evaluated through observations of the activity levels of RIFA mounds and abundance. The effects of RIFA on other ant species were determined by eliminating RIFA with insecticides, and then sampling for all remaining ant species. Measurements of RIFA mound activity was done by recording their response to the vibration of wire flags located in active mounds. This method indicated control of RIFA with hydramethylnon and metaflumizone from 61 to 180 d post-treatment. Additional monitoring for RIFA activity, in the same plots, was done with baited vials. These results indicated that complete control of RIFA was never achieved with either hydramethylnon or metaflumizone within 180 d post-treatment; however, there were significant reductions in RIFA population as a result of both chemical baits from 3-92 d post-treatment. A reduction of RIFA populations occurred with both baits, as determined through scheduled sampling of all ant species using baited vials. Native ants, such as Dorymyrmex spp., were found in higher numbers once RIFA populations were reduced, indicating that the two ant species compete for resources such as food and space. Dorymyrmex spp. numbers were suppressed by RIFA populations, while other ants, such as Paratrechina spp. were unaffected.

Solenopsis invicta is an invasive ant that has caused detrimental impacts to ecosystems and economies in the Southeastern United States, recently including Virginia. In this study, we explored the invasion ecology of S. invicta through two main objectives. First, we established a comprehensive distribution map of S. invicta in Virginia through multiple survey techniques. We then compared our findings with published models quantifying the potential spread of S. invicta and created our own species distribution model. In 2020-2021, S. invicta occurrences were found in 7 counties beyond the current Quarantine and our data show that S. invicta has spread further than predicted. Our own species distribution model suggests that the distribution area for S. invicta is likely to increase under the projected climate change. This study provides insights into the range expansion of S. invicta at the border of its suitable habitat and allow for improvements to models of its spread under these conditions. Additionally, it provides useful information to inform county extension agents to know where they are to expect new infestations of S. invicta. Second, we investigated the impacts of pesticide residue on the behavior of S. invicta through neonicotinoid exposure. We found detectable levels of neonicotinoids in the soil of the ant mounds as well as in the ants themselves. In addition, we investigated the effects of dietary exposure to imidacloprid on foraging behavior in a laboratory setting. We found that unexposed colonies were able to locate the food source more quickly during the second trial while exposed ants were unable to improve their performance. We also found that more exposed ant workers were unable to successfully navigate the maze as compared to unexposed workers. Our results suggest impaired learning of maze tasks and impaired navigational skills in neonicotinoid-exposed ants. / Master of Science in Life Sciences / The red imported fire ant (RIFA) is an invasive ant species found throughout the Southeastern United States that has negatively impacted ecosystems and economies. In the past few decades, RIFA has invaded the Coastal Plain of Virginia, resulting in legislation that restricts the movements of soil, plant products, and some equipment in and out of several southeastern counties and independent cities. To develop better management practices, there is a critical need to understand the spread, establishment, and impacts of RIFA in greater detail. We aimed to do this by surveying the current distribution of RIFA in Virginia and investigate the impact of insecticide use on their spread and behavior. In 2020-2021, we found RIFA occurrences in 7 counties beyond the current Quarantine, which is further than previously predicted. We then built a model using climatic variables that predicts the distribution of RIFA and found their habitable range is likely to increase under the projected climate change. Additionally, we investigated the impacts of common agricultural pesticides on the behavior of RIFA. We found these chemicals present in both the soil of the ant mounds and in the ants themselves. We also found that dietary exposure to imidacloprid, a neonicotinoid pesticide, altered the foraging behavior of RIFA. This study provides useful information to advise county extension agents to know where they are to expect new infestations of RIFA. Our results also suggest that human activity alters the invasion ecology of recent arrivals such as the red imported fire ant.

Solenopsis invicta, the red imported fire ant, has recently become associated with Antonina graminis, an invasive pest, and Neodusmetia sangwani, biological control agent, and maybe negatively affecting established biological control. A preliminary survey outlined the range of A. graminis and its parasitoids, and found N. sangwani was present at a reduced rate in South Texas and in the southeastern United States. A greenhouse experiment demonstrated that S. invicta decreased the rate of parasitism of A. graminis by N. sangwani, with S. invicta directly interfering with oviposition. Interactions between S. invicta and A. gaminis may be facilitating the spread and establishment of two invasive pests which has a negative impact on established classical biological control of A. graminis by N. sangwani.

Solenopsis invicta, the red imported fire ant, has recently become associated with Antonina graminis, an invasive pest, and Neodusmetia sangwani, biological control agent, and maybe negatively affecting established biological control. A preliminary survey outlined the range of A. graminis and its parasitoids, and found N. sangwani was present at a reduced rate in South Texas and in the southeastern United States. A greenhouse experiment demonstrated that S. invicta decreased the rate of parasitism of A. graminis by N. sangwani, with S. invicta directly interfering with oviposition. Interactions between S. invicta and A. gaminis may be facilitating the spread and establishment of two invasive pests which has a negative impact on established classical biological control of A. graminis by N. sangwani.

Ants are capable of building close associations with plants, insects, fungi and bacteria. Symbionts can provide essential nutrients to their insect host, however, the development of new molecular tools has allowed the discovery of new microorganisms that manipulate insect reproduction, development and even provide defense against parasitoids and pathogens. In this study we investigated the presence of bacteria inside the Red Imported Fire Ant midgut using molecular tools and transmission electron microscopy. The midgut bacteria were also characterized by their morphology, biochemical activity, and antibiotic resistance profile. After isolation, culture, and characterization of these bacteria, the molecular analysis revealed ten unique profiles which were identified to at least the genus level, Enterococcus sp./durans, Klebsiella ornithinolytica, Kluyvera cryocrescens, Lactococ-cus garvieae, Pseudomonas aeruginosa, Achromobacter xylosoxidans, Bacillus pumilus, Listeria innucua, Serratia marcescens, and an uncultured bacterium from the Entero-bacteriaceae. New SEM and TEM techniques revealed a possible functional association of endosymbiotic bacteria with the insect host, and it also showed the absence of bacteriocytes in the epithelial cells of the midgut. The PCR results, from the bacteria abundance and distribution studies, showed that Enterococcus sp., Kluyvera cryocres-cens and Lactococcus garvieae are the most abundant species, but they are not consistently found in all sites throughout the southeastern United States. Kluyvera cryocrescens, Serratia marcescens, and an uncultured bacterium (isolate #38: Enterobacteriaceae) were genetically modified with the plasmid vector pZeoDsRed and successfully reintroduced into fire ant colonies. Strong fluorescence of DsRed was detected up to seven days after introduction. The transformed bacteria can still be rescued after pupal emergence; however most were passed out in the meconium. We further demonstrated that nurses contributed to the spread of the transformed bacteria within the colony by feeding the meconium to naive larvae. Although the role of midgut bacteria in the fire ant is still unknown, we have no indication that they cause any pathology. Studies emphasizing the role of these bacteria in fire ant physiology are still ongoing. These results are the foundation for a fire ant biological control program using endosymbiotic bacteria as vectors to introduce foreign genes that express proteins with insecticidal properties.

I examined the impacts of the invasive red imported fire ant (RIFA, Solenopsis invicta) on native ants (Monomorium minimum, Paratrechina sp., S. krockowi, Pheidole metallescens, Forelius pruinosus, and Camponotus americanus) and litter removal in a post oak savannah community in central Texas. The study site was divided into 3 adjacent areas, and ant-toxic bait was used, along with additional colonies of RIFA, to establish 3 different densities of RIFA (naturally occurring, low, and high). I surveyed the ants in the 3 density areas and calculated the catch per unit effort for each species. Litter baits were placed in the 3 density areas for 14 12-hour trials. The masses of the litter removed were measured, and means were calculated for each speciesdensity/ trial/date/period/bait combination. The average amounts of litter removed by RIFA and native ant were different in the 3 density areas (0.42 g, 0.0 g, and 0.75 g for RIFA in the natural RIFA density area, low RIFA density area, and high RIFA density area, respectively; 0.0 g, 0.16 g, and 0.15 g for native ants in the natural RIFA density area, low RIFA density area, and high RIFA density area, respectively), indicating that RIFA does have an effect on native ant habitat use.

This research evaluated the new red imported fire ant (RIFA) bait Advion™. Advion™ contains the active ingredient indoxacarb which, following ingestion, must be metabolized into an N-decarbomethoxyllated metabolite known as JT333 in order to become acutely toxic. Laboratory experimentation was conducted to determine the most effective chemical form and concentration of indoxacarb, as well as the most appropriate grit size, for use in Advion™. The results indicated that Advion™ containing indoxacarb was more effective than Advion™ containing JT333, that 0.10%, 0.06%, and 0.045% were the most effective concentrations of indoxacarb, and that standard sized grit (~2 mm) was more effective than small sized grit (<1 mm). Field experimentation was conducted to determine the most effective concentration and quantity of Advion™, as well as the most effective placement of the bait, for obtaining maximum control of RIFA colonies via individual mound treatments. The results indicated that 10 g (2 Tbsp) of 0.045% Advion™ placed around the mound in a circle with a radius of 0.5-3.0 m was the most effective manner in which to treat individual RIFA mounds. Field experimentation was also conducted to compare the effectiveness of label-rate broadcast treatment with Advion™ to the effectiveness of both label-rate broadcast treatment with Amdro® and pre-baiting broadcast treatment with Advion™. Both pre-baiting broadcast treatment and label-rate broadcast treatment with Advion™ ultimately resulted in 98-99% RIFA colony mortality, which was significantly greater than the 87% colony mortality resulting from broadcast treatment with Amdro®. The 6.2 d LT90 for label-rate broadcast treatment with Advion™ was nearly one half that of the LT90 for pre-baiting broadcast treatment. Laboratory experimentation was conducted to determine whether RIFA workers were capable of metabolizing indoxacarb into the toxic metabolite, and the results clearly indicated that they were. Finally, field experimentation was conducted to evaluate the effectiveness of label-rate broadcast treatment with Advion™ at controlling multiple ant species. The results indicated that label-rate broadcast treatment with Advion™ resulted in control of the RIFA and Pogonomyrmex barbatus for at least 7 wk, and Monomorium pharaonis and Dorymyrmex pyramicus for some period of time between 3 and 7 wk.