The Argentine ant, Linepithema humile, is a widespread invasive species characterized by reduced intraspecific aggression within its introduced range. To gain an understanding of mechanisms underlying nestmate recognition in the Argentine ant, I studied its population genetic structure and the role of genetic vs. environmental cues on aggression. I combine behavioral, genetic, and analytical data to explore the role of exogenous cues and recent changes in the population genetic structure on nestmate recognition in this ant. In Chapter II, I examined population genetic structure and intercolony aggression in two portions of the Argentine ant introduced range: California and the southeastern U.S. I describe factors that may have contributed to the present-day differences in genetic diversity between these two regions and I also suggest ecological factors that may have contributed to regional differences in current distribution patterns of the Argentine ant. In Chapter III, I examined the context-dependency of nestmate discrimination in the Argentine ant and the effect of action thresholds on exogenous cue recognition. I also tested hypotheses that explain a change in action thresholds as well as factors that affect action thresholds. I examined changes in intraspecific aggression in various discrimination contexts. I tested the importance of isolated nest referents on aggression thresholds. In Chapter IV, I examined the impact of different diet-derived hydrocarbons on intraspecific aggression in the Argentine ant and the potential of shared, diet-derived hydrocarbons to produce colony uniformity where intercolony genetic and/or environmental differences exist. In Chapter V, I examined the role of environmental cues on nestmate recognition in two populations of the Argentine ant. I tested the hypothesis that there is geographical variation in the response of Argentine ants to nestmate recognition cues derived from prey. In Appendix I, I use the Argentine ant to compare four aggression bioassays for consistency between replicates, similarity between assays, and ability to predict whole colony interactions. I tested four different aggression assays with two or three scoring methods per assay. I also determined whether isolated aggressive encounters could predict whole colony interactions.

Biological control, host resistance, and vegetative propagation were evaluated as management strategies for the exotic pest hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae) in the southeastern U.S. Biological control studies focused on the adelgid predator Sasajiscymnus tsugae Sasaji and McClure. In the laboratory, the suitability of an alternative prey species balsam woolly adelgid (BWA), Adelges piceae Ratz., for predator feeding, oviposition, immature development, and long-term survival was compared to the primary prey HWA. The BWA was found to be a suitable host to support predator feeding and development but was found to negatively influence S. tsugae survival. Field studies of S. tsugae tested the utility of multi-point, low-density, confined releases in mesh sleeve cages as an alternative to a routinely utilized single-point, high-density, free release for introducing the predator to forest and ornamental sites in Western North Carolina. The studies found that S. tsugae will reproduce inside sleeve cages and can survive for up to one month in confinement, but field establishment of the predator could not be confirmed. In the greenhouse a method for artificially inoculating hemlock seedlings with HWA and comparing levels of host resistance among hemlock species was tested. Using this method, initial infestation rates and fecundity of HWA were compared among three species of hemlock native to North America: eastern hemlock (Tsuga canadensis), Carolina hemlock (T. caroliniana), and western hemlock (T. heterophylla). Infestations were significantly and four-fold higher on eastern hemlock compare to those on Carolina and western hemlock that did not differ. A second greenhouse trial assessed the rooting ability of softwood stem cuttings from mature specimens of eastern and Carolina hemlock. The study found that eastern hemlock cuttings rooted best with no hormone applications and at higher rates than Carolina hemlock which required very low concentrations of auxin.

The Empidoidea are a monophyletic superfamily of flies that includes dance flies (Empididae), long-legged flies (Dolichopodidae), and several small families (Atelestidae, Hybotidae, and Brachystomatidae). Empidoids are found worldwide and contain many thousands of species, but none have ever been described from Madagascar. An ongoing biodiversity survey by the California Academy of Sciences has brought to light many hundreds of undescribed empidoids from the island. This research project involves description, databasing, and DNA barcoding to establish the first estimates of empidoid species diversity in Madagascar. This study will contribute to critical surveys of species richness for rapidly degrading habitats in this important biodiversity hotspot. Representatives from two empidoid families, Empididae and Hybotidae were collected from Madagascar. There are eight new species of Hybos (Hybotidae: Hybotinae) from Madagascar: H. gardneri sp. nov., H. flaviarticulus sp. nov., H. verykoukis sp. nov., H. fianarantsoensis sp. nov., H. exastis sp. nov., H. triangulus sp. nov., H. angustifacies sp. nov., and H. ignotopalpus sp. nov. All species are described and male genitalia are illustrated. DNA barcoding was performed on the flies from the subfamily Hybotinae in order to infer species limits, but due to poorly preserved or degraded DNA, no definitive conclusions could be drawn. To aid identification, eight new barcodes were obtained that will be submitted to the barcode library upon publication of the new species. All data collected for the Madagascar empidoids have been recorded in a Mandala database and all images have been uploaded into Morphbank. Additionally, a LucID key is available on the Internet for species identification.

Invasive species have major impacts on the ecosystems they invade. Among the most disruptive groups of invasive species are ants. Invasive ants have caused losses in biodiversity among a wide range of taxa, including birds, mammals, lizards, but especially towards ground nesting arthropods such as native ants. Why native ants are so susceptible to invasion and how invasive ants are able to sustain massive population growth remain unclear. It has been suggested that invasive ants utilize carbohydrate resources from hemipteran exudates to fuel aggressive foraging and colony expansion. Perhaps invasive ants are simply more proficient at usurping these resources, maintaining higher hemipteran populations, etc. Our work uses a model invasive, the Argentine ant, , Linepithema humile, and a native ant Tapinoma sessile to quantify hemipteran tending ability and competition. Through a series of laboratory and field experiments we were able to quantify 1) carbohydrate sequestering performance, 2) the effect either ant species had on hemipteran population growth rates in a predator-free space, 3) the defense ability of either ant against hemipteran predators and parasitoids, and 4) the proportion of invasive ants required to displace a native colony from a hemipteran resource. Neither ant demonstrated a better ability to sequester liquid resources; however recruitment strategies were much different. Hemipteran populations in the presence of L. humile grew larger in a predator free environment and populations exposed to predators were better defended by L. humile than T. sessile. L. humile was able to displace T. sessile from a nest site without having a majority of worker ants. Aggression of either ant species was significantly reduced without hemipterans present. Understanding factors that drive invasive species can give us insight into native areas that may be susceptible for invasion, how potential mutualist populations might respond and possibly provide us with an avenue for secondary control measures given the economic and ecological importance of invasive species.

Bovine serum albumin (BSA) and anti-BSA polyclonal antibody were used as model polypeptides to examine protein movement across the insect digestive system and cuticle and their accumulation in hemolymph of fourth stadium tobacco budworms, Heliothis virescens. The use of hydrateable meal pads to deliver a specific concentration of these two proteins in insect diet was investigated. Continuous feeding on artificial diet containing 0.8 mg of anti-BSA/g hydrated diet resulted in 2430±125 and 3459±105 ng of anti-BSA/mL hemolymph after 8 and 16 h, respectively (average ± 1 SEM), as determined by ELISA. Continuous feeding on meal pads with the same concentration of BSA resulted in 1547±132 and 1623±122 ng of BSA/mL hemolymph at 8 and 16 h, respectively. No BSA or anti-BSA was found in the feces, and when 5 mg of these two proteins were applied topically in DMSO to the cuticle, neither protein was found in the hemolymph after 4 h. Western blot analyses using native and/or de-naturing gel electrophoresis demonstrated that both BSA and anti-BSA were not degraded in the hydrated meal pads and were also unchanged in the hemolymph, retaining the multimeric structure for BSA and the antigen reactivity for anti-BSA. When 1 mg of anti-BSA or BSA was injected into the hemocoel of fourth instars, the concentrations decreased with time and 120 min after injection were 0.6 and 20% of the original concentration, respectively. When added at the same original concentration to hemolymph in vitro, the decrease was 81.5 and 57.5%, respectively, at 120 min. Apparently, the accumulation of native anti-BSA and BSA protein in insect hemolymph is the result of the rate of their transfer from the diet versus their rate of turnover in the hemolymph. Hemolymph turnover of these proteins appears to be the result of degradation and sequestration.

Porcine Reproductive and Respiratory Syndrome (PRRS) is a globally significant viral disease of swine. The link between outbreaks in separate farms within an area remains unclear despite biosecurity measures. We have investigated the vector potential of stable flies in the transmission of PRRSV under laboratory conditions. We first determined that blood seeking stable flies are attracted to pigs by olfactory cues. We determined stable flies could acquire the virus through a bloodmeal, and the amount of virus in the flies declined with time, indicating the virus does not replicate in fly digestive tissues. Transmission of the virus to naïve pigs failed in all attempts. The volume of blood contained in the closed mouthparts of the stable fly appears to be insufficient to deliver an infective dose of the virus. We further examined the fate of PRRS virus in the hemolymph of the flies following a midgut barrier bypass. Virus levels were up to 9,500 times greater in the hemolymph when compared to those detected in the digestive tract at the same time point. Further study to test the saliva of inoculated stable flies for presence of the virus is needed to determine if PRRS virus can enter and escape stable fly salivary glands. Although stable flies are unlikely vectors of PRRS virus between animals, they may play a role in virus dissemination by harboring the virus and contaminating the environment.

The purpose of this research was to obtain background information to aid the implementation of a biological control program against the weed, kudzu (Pueraria montana var. lobata Willd). This research had several specific objectives that examined: 1) potential insect pollinators and seed production of kudzu in NC; 2) phytophagous insects and insect herbivory of kudzu foliage, seeds, vines and roots in NC; 3) abundance and diversity of foliar, vine, and root feeding insect communities on kudzu in comparison with those found on soybeans, the closest North American relative of kudzu in the United States. Kudzu is pollinated by native and naturalized insects in NC, in a pattern that varies by flower apparency rather than density. Arthropod herbivory by native generalists almost eliminated kudzu seed viability, while a naturalized Asian specialist consumed a nominal proportion of seeds. These data indicate that seed feeding arthropods would be poor candidates for importation biological control. Kudzu and soybeans shared the same foliar feeding insect communities and levels of defoliation, suggesting that foliage feeders are also poor choices for importation. No kudzu vine or root feeding insects or damage were found during the two years of this study, suggesting that future importation biological control research should focus on such feeders from Asia.

<p>The purpose of the research has been to further the understanding of the seasonal occurrence of tomato spotted wilt virus (TSWV) and the insect vector, Frankliniella fusca, in relation to North Carolina peanut production. Emphasis was placed on 3 Virginia-type peanut genotypes, NC-9, NC-V11, and NC-12C, which were included in field and greenhouse experiments to determine relative disease and thrips levels and their interactions. These are components of a larger strategic goal to develop management strategies that can minimize future impacts of TSWV and be compatible with peanut production in North Carolina. Research was conducted to determine the winter, spring, and summer occurrence of F. fusca in NC peanut fields. Thrips movement in spring was significantly influenced by prevailing wind direction. No thrips were collected on sticky traps during days when maximum temperature did not exceed 18.7 C. F. fusca, caged with TSWV infected peanut plants in August, 1996 and sampled in March, 1997, were analyzed for the presence of TSWV by ELISA. A single thrips tested positive for the virus. In another experiment, three Virginia-type peanut genotypes were monitored for the incidence of TSWV symptoms and the presence of F. fusca at 3 locations in NC's peanut producing area. Overall disease incidence at the 3 locations was 6%. Of the genotypes, NC-9 ranked the highest in disease incidence (7%), followed by the genotypes NC-12C (6%), and NC-V11 (5%). F. fusca counts were greatest on NC-V11, followed by NC-9 and NC-12C. A comparison of the survival and reproductive success of F. fusca on TSWV infected and uninfected plants of the 3 genotypes was conducted under greenhouse conditions in NC. Effects of genotype and virus by genotype interaction were not significant. However, TSWV infected plants had significantly fewer adult and larval F. fusca than did uninfected plants.<P>

<p>Horizontal movement of the insect growth regulator (IGR) pyriproxyfen to larval microcosms by gravid container-inhabiting mosquitoes, Aedes albopictus (Skuse) and Aedes triseriatus Say, was evaluated under laboratory conditions. In larval susceptibility bioassays determining emergence inhibition (EI), both species were found to be highly susceptible to the IGR. Aedes albopictus exhibited an EI50 of 0.200 ppb, while Aedes triseriatus was 7 and 3.5x more susceptible with an EI50 of 0.0288 ppb. A randomized complete block experimental design was used for each species to evaluate the horizontal transfer of the IGR by gravid females force contacted with pyriproxyfen-treated oviposition strips. For Ae. albopictus, experiments were blocked by treatment rate of pyriproxyfen (0.2, 0.3 and 0.4 mg/cm2). Effects of numbers of treated females (1, 3 and 5 females per bioassay cage) on horizontal movement of the IGR was evaluated within each treatment rate. One treatment rate of pyriproxyfen (0.2 mg/cm2) was evaluated for Ae. triseriatus. A significant (P<0.05) curvilinear response in emergence inhibition was observed in Ae. albopictus and Ae. triseriatus over the three population densities of treated females evaluated. Notably, the shape of the response curves for the two species were opposite. Lower but equivalent levels of mortality were achieved at densities of 1 and 3 treated Ae. triseriatus females per cage with significantly higher levels of inhibition of emergence observed at 5 females per cage. At 1,3, and 5 females per cage, mortality of Ae. triseriatus averaged 20.8%, 26.9%, and 70.4%, respectively. For Ae. albopictus, mortality at the higher two population densities was similar and significantly larger than was observed at the lowest population density. Mean mortality of Ae. albopictus ranged over the 3 treatment rates from 3.5 to 30.2%, 47.8 to 67.3%, and 58.6 to 73.1% at densities of 1,3 and 5 females per cage, respectively. Amounts of pyriproxyfen transferred by gravid females were estimated from the log dose-probit mortality data obtained in larval bioassays.In binary choice bioassays, horizontal transfer of biologically active amounts of pyriproxyfen from treated (0.3 or 0.4 mg/cm2) to untreated microcosms was achieved by Aedes albopictus. Three microcosm configurations were utilized in an attempt to manipulate mosquito oviposition behavior to increase the amount of IGR transferred. Emergence inhibition (37.8%) for microcosms completely wrapped in black paper was significantly higher (P>0.05) than two other configurations utilized. Forcibly exposing gravid females to pyriproxyfen-treated surfaces did not affect their fecundity. However, mean percent egg hatch between egg clutches laid in the 1st and 2nd gonotrophic cycles declined significantly (P<0.05) by 30%. To assess the residual activity of pyriproxyfen, 1st instar Ae. albopictus were added to microcosms used in forced-contact experiments. Mosquito mortality declined markedly indicating that pyriproxyfen was not highly residual in larval microcosms. Use of IGR-treated oviposition containers to achieve horizontal movement of pyriproxyfen to mosquito oviposition sites in the field is a promising management technique. However, laboratory results were often variable, suggesting that interactions between females within the oviposition site caused a differential transfer of pyriproxyfen to larval microcosms. Comparative studies of the oviposition behavior of each mosquito species are warranted and would potentially provide information needed to improve the technique.<P>

<p>Field experiments were conducted to investigate the effects of Cry1Ab toxin of Bacillus thuringiensis expressed in transgenic sweet corn (Attributeä) on larval dispersal and larval density of the fall armyworm, Spodoptera frugiperda (Smith), which could affect rates of adaptation to Bt corn. Crop phenology and agronomy were also tested to determine the affects of rapid corn maturation and tillers on insect survival. Behavior and dispersal of larvae from the neonate to 10 day-old larval stage was measured in single variety plots of Bt and conventional plants. Each plot was artificially infested with one egg mass to test the hypothesis that Bt toxins affect larval behavior, increasing dispersal of early instars. Results indicated that crawling behavior of neonates was similar in both varieties but larvae settled faster on conventional plants. Larval dispersal among plants was also statistically similar in both varieties at all sampling dates. In separated plots, two larval densities and three planting dates were studied. Mortality of fall armyworm larvae in Bt sweet corn was not density-dependent. Early entry of the corn plant into reproductive stage apparently affected larval survival. There is not differential larval utilization and survival in tillers versus main whorls of Bt and non-Bt plants. Insect adaptation to Bt toxins is likely affected by larval dispersal and rapid maturation of corn plants.<P>