A molecular and genetic dissection of the stalled grooming mutant was performed to characterize a gene which may be necessary for the assembly of the pupal and adult nervous system of Drosophila melanogaster. To determine whether the grooming deficit observed in stalled resulted from disrupting the development of the sensory nervous system, afferent projections were examined in stalled using two P (Gal4) lines as markers of subsets of femoral chordotonal neurons. These lines were isolated in a screen of P (Gal4) enhancer trap lines to identify those which label distinct subsets of sensory neurons and their afferent projections in the pupal and adult nervous system (Chapter 1). In addition, afferent projections from the posterior tactile neurons were examined in stalled mutants using the en-lacZ marker line. Because the stalled P element insertion site was mapped to the 67C region of the third chromosome (as was the laminin $\gamma$ gene), it was of interest to determine whether stalled had identified $laminin\ \gamma$ since it has been demonstrated that the laminin plays roles during neuronal development. It was possible that stalled would interact with $laminin\ \alpha$ as a result of identifying the $laminin\ \gamma$ gene. Therefore, a genetic analysis was performed by combining stalled with the $laminin\ \alpha$ mutant and examining projections from different classes of sensory receptors in the single and double mutants. It was found that the interaction with stalled and $laminin\ \alpha$ was required for the proper development of at least two classes of sensory receptors (Chapter 3). Therefore, molecular characterization of stalled was performed to determine if stalled had identified the $laminin\ \gamma$ gene. Northern analysis demonstrated that the expression of $laminin\ \gamma$ was decreased in stalled and the $stalled\sp{e71}$ hypomorph. However, mapping experiments demonstrated that the stalled P element insertion site was 20-60 kilobases downstream of $laminin\ \gamma$. Taken together, these results suggest that stalled has identified an enhancer of the $laminin\ \gamma$ gene such that the amount of the laminin heterotrimeric complex is reduced in the $laminin\alpha;stld$ double mutants. This results in significant effects on the development of at least two distinct classes of sensory afferent projections.

The banana weevil, Cosmopolites sordidus (Germar), is the most important constraint to banana production in East African highlands. For most resource-poor farmers in the region, biological control is the only viable option because it requires little or no cash investment. I investigated patterns of predation by natural enemies of the banana weevil in its presumed native range in Indonesia to determine if there were natural enemies that could be imported to control the pest in Africa. Work was also done in Uganda to determine if predatory insects already present in local banana farming systems could be better conserved to produce banana weevil control. Through farm surveys in Indonesia, I confirmed existing reports that banana weevil damage is low in Sumatra and Java. However, I found no evidence of parasitism from 25,000 eggs and 3600 larvae collected from seven diverse geographical locations. The adult and larvae of the histerid, Plaesius javanus Erichson, were found to be important predators of C. sordidus. P. javanus larva entered tunnels of plants, presumably in search of banana weevil stages. This predator should be imported to Uganda for establishment as a classical biological control agent of the banana weevil. Experiments in Uganda showed that destruction of crop residues in bananas, as recommended for weevil control and practiced by some farmers, reduced predator numbers on farms, reduced predator: prey ratios and had no benefit to the plant with respect to damage prevention. Instead, I demonstrated that residue presence, through maintaining high predator: prey ratios, offsets damage to plants that would otherwise occur from increased numbers of banana weevils. Ants are the major predatory group now present in banana farming systems in Uganda. Surveys in banana farms found 55 species from pitfall traps, 17 from banana pseudostem residues and 34 from banana corms. Eleven species of ants came to banana weevil egg and larvae exposed in the field as baits and thirteen species were tested in the laboratory for their potential to attack the banana weevil. Two species—Pheidole sp. 2 (Myrmicinae) and Odontomachus troglodytes (Santschi) (Ponerinae)—caused significant banana weevil larvae mortality in crop residues and significant egg mortality in living plants in microcosm experiments and in the field.

In the first chapter, I introduce the study organisms, non-biting midges in the genus Axarus. These are large flies that spend the majority of their lifespan living aquatically in submerged clays and rotting wood in the Connecticut River. The adult lifespan is very brief, on the order of three days, while the larvae live for one year. There are two species so far discovered in the Connecticut River, both new to science, and very closely related to each other. Both species coexist in distinct populations separated by areas where there is no suitable habitat for them; the primary habitat being clay that was deposited during the existence of glacial Lakes Hitchcock and Coös, with a secondary use of rotting wood also evident. The population genetic evidence indicates that wood is only inhabited near clay deposits though, and there is genetic separation between the populations, a fact that is established in Chapter 3. Chapter 1 provides the foundational biological information necessary to use these species in a study of population genetics. In the second chapter I show that populations of one of the species, herein referred to as A. species varvestris, is polymorphic for 4 chromosomal inversions, and that natural selection is acting on one of these inversions. The inversion in question results in a significant decrease in larval size when heterozygous, and increases in frequency within one generation. This is evidence of natural selection, and size-selective predation is suggested as a mechanism for the selection. An association between this inversion and the sex determination of the species is also shown. The third chapter presents a large dataset of chromosomal mutation frequencies that establishes marked cytogenetic differentiation between the populations of Axarus species varvestris. I suggest that this differentiation has occurred within a very short time-frame, on the order of 10,000 generations, and that the structure of the population cytogenetic relationships may reveal and be correlated with the ancient separation between the post-Pleistocene lakes that were present in the river valley following the last ice age. (Abstract shortened by UMI.)

An improved in vitro rearing system, based on a silicone-reinforced Parafilm® M membrane, human hair tufts and reconstituted human blood, enabled the large-scale rearing of pediculicide-susceptible (EC-HL) and resistant (FL-HL and BR-HL) strains of human head lice. Developmental time differed for early instars but differences became synchronized as lice matured. Mean survivorship amongst the three strains reared in vitro were not significantly different when compared to EC-HL and FL-HL reared in vivo. FL-HL and CA-HL were resistant to permethrin compared with susceptible PAHL (5.5- and 3.4-fold, respectively) and EC-HL (8.5- and 5.3-fold, respectively). Permethrin-resistant lice were cross-resistant to pyrethrum and DDT. Permethrin resistance was synergized by piperonyl butoxide (PBO) in CA-HL. Resistance to malathion in FL-HL (1.4- to 2.2-fold) and CA-HL (2.1- to 3.6-fold) was detected. Malathion resistance in FL-HL was synergized by S.S.S-tributylphosphorotrithioate (DEF) and by PBO in CA-HL. Malathion/permethrin-resistant BR-HL lice were synergized by DEF but not synergized by PBO. PBO protected BR-HL from malathion, indicating suppressed desulfuration. Abamectin resistance in FL-HL (1.7- to 2.5-fold) and CA-HL (1.8- to 2.3-fold) was detected. No resistance to lindane was found. Thus, multiple resistance mechanisms against commonly available and widely used pediculicides and insecticides are apparently occurring. Results from linkage analysis substantiate that permethrin resistance in human head louse populations in the U.S. is widespread but occurs at varying frequencies. The log survival time versus logit mortality regression lines of susceptible-homozygotes, resistant-homozygotes and heterozygotes determined that the resistance trait was complete recessive. Permethrin resistance is highly correlated with the presence of the T917I and L920F point mutations, which are suitable for detection by a variety of DNA-based diagnostic techniques. Electrophysiological assessments determined that the three mutations (M815I, T917I and L920F) associated permethrin- and DDT-resistance in head louse caused depolarizing shift of ∼3.2 and ∼8.8 mV in the voltage dependent activation and steadystate inactivation, respectively, and completely abolished permethrin sensitivity when correspondingly inserted into house fly para-orthologous, voltage sensitive sodium channel and expressed in Xenopus oocytes (M827I, T929I and L932F). Amongst these kdr mutations, T929I appears to be the major resistance-causing mutation.

Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) is the most important insect pest for greenhouse flower crops. Thripinema nicklewoodi Siddiqi (Tylenchida: Allantonematidae) is an entomoparasitic nematode attacking and sterilizing the thrips. Methods to propagate and study T. nicklewoodi were developed. I observed an excretion rate of 21.4 nematodes per day by parasitized female thrips. The sex ratio of the excreted nematodes was 6:1 (female:male). After exposing 50 healthy first instars to four parasitized female thrips in a rolled bean leaf, I obtained a 75.3% mean parasitization rate in the adult stage of the thrips. In contrast to previous reports, male thrips were found to be parasitized as readily as females. Parasitism reduced the longevity of both adult female and male thrips by 26% and 61%, respectively. T. nicklewoodi when presented with various thrips life stages achieved the highest attack rate in first and second instars and prepupa. Free-living nematodes were found to escape from hosts through the anus and penetrate new host thrips through the intersegmental membranes of the thorax and abdomen. While nematode parasitization affected tospovirus propagation, it did not reduce transmission of impatiens necrotic spot virus even though parasitism reduced feeding activity of adult female thrips by 81% on leaves, 38% on pollen, and 22% on honey. However, despite lowered total feeding, probing by parasitized thrips (in honey) was not reduced, and this may explain why lowered feeding does not result in lowered virus transmission. In a study of the population dynamics on caged impatiens in greenhouse, nematode transmission persisted for seven host generations and populations of normal (i.e., not parasitized) female thrips declined by 39–79% in the nematode treatment compared to the control. However, no significant reductions were found in numbers of larval thrips between nematode treatments and the control. A higher proportion of male thrips occurred in populations with nematodes in which adult female thrips declined significantly compared to the control population. T. nicklewoodi released seven times on caged impatiens in a greenhouse did not provide preventative control of thrips, though the population growth of second instar, adult female, and male thrips was suppressed by 44, 68, and 49%, respectively.

While pollinators and leaf herbivores have been a focus of research for decades, floral antagonists have been studied significantly less. Since floral antagonists can be as common as leaf herbivores and have strong impacts on plant reproduction, it is important to understand the role of floral antagonists in the ecology and evolution of flowers. I conducted four experiments to better understand the relationship between plants, floral traits, floral antagonists, and other plant-insect interactions. First, I manipulated resources (light and soil nutrients) that are known to have impacts on plants and floral traits to test how they affect floral antagonists and other plant-insect interactions. Plentiful resources increased the proportion of floral antagonists to visit flowers, but also increase tolerance of floral antagonists. Second, I manipulated flower bud gallers, a species-specific floral herbivore that destroys flowers, to test how it affected other plant-insect interactions, floral traits, and plant reproduction. Plants with flower bud gallers tended to have more pollinator visits, but this effect is due to a shared preference by gallers and pollinators for similar plants. Third, I manipulated florivory to examine how it affects subsequent plant-arthropod interactions, floral traits, and plant reproduction. Florivory had systemic effects on other plant-insect interactions, including leaf herbivores, and shifted the plant mating system towards more selfing. Additionally, I tested how several floral antagonists respond to floral attractive and defense traits to understand which floral traits are important in mediating antagonisms. Finally, I manipulated florivory, pollination, and nectar robbing to test for effects of multiple floral interactions on subsequent plant-insect interactions, floral traits, and plant reproduction. There were significant many-way interactions between the three treatments on subsequent plant-insect interactions and reproduction, indicating that the effect of one interaction depends on what other interactions are present. Understanding the role that floral antagonists play in plant ecology can help scientists determine which interactions are most important, and may help determine why some floral traits exist in their current state. Together, this work represents some of the most comprehensive research on the community consequences of floral antagonists, as well as the interplay between floral traits and floral interactions.

Cranberry tipworm, Dasineura oxycoccana Johnson (a gall-making fly), disrupts normal growth of cranberry (Vaccinium macrocarpon Aiton) by injuring the apical meristem of shoots or uprights. The impact of larval feeding injury on reproductive parameters of cranberry was determined, from one growing season to next, at upright (Maine and Massachusetts, 2008–2009) and plot levels (Massachusetts, 2009–2010 and 2010–2011). I also estimated the proportions of uprights injured because of tipworm feeding at several cranberry production sites (Massachusetts and Maine) and the proportions of uprights that produced flowers and fruits in the next growing season. Tipworm-injured uprights tagged at the end of the growing season did not produce floral-units (following year) across sites in both Massachusetts and Maine. There was significant variation among the sampled sites in the proportions of tipworm-injured uprights and also in the proportions of uprights with flowers in the next growing season (Massachusetts and Maine). A trend was apparent wherein sites with higher tipworm injury levels had relatively lower flowering proportions in the next growing season. However, sites in Massachusetts did not differ in the proportions of uprights that set fruit and in a replicated study, significant reduction in tipworm injury at plot level (using insecticide) did not impact flower and fruit production in the next growing season. A two-year field study was carried out at three different locations to determine the impact of tipworm feeding injury on the reproductive and vegetative growth of two cranberry cultivars ('Howes' and 'Stevens') in Massachusetts. Individual uprights of cranberry exhibited tolerance to natural (tipworm) and simulated apical meristem injury in the current growing season (fruit production) and results were corroborated by a greenhouse study. In the field study, weight of fruit was higher in tipworm-injured uprights as compared with intact control uprights at the sites with Howes. However, majority of injured uprights (tipworm and simulated) did not produce new growth from lateral buds (side-shoots) before the onset of dormancy. In the next growing season, fewer injured uprights resumed growth and produced flowers as compared with intact uprights at two of the three sites.

The gypsy moth, Lymantria dispar L., is one of the most damaging pests of the deciduous forests in the United States. It was accidentally introduced from Europe in 1868 by an amateur naturalist in eastern Massachusetts. High density gypsy moth populations are regulated primarily by a nuclear polyhedrosis virus (LdNPV). LdNPV is transmitted by feeding the LdNPV contaminated foliage or the contaminated egg chorion on the way out from the egg by a larva. In 1989, an entomophthoralean fungus, Entomophaga maimaiga Humber, Shimazu et Soper was discovered in the northeastern United States, which caused massive epizootic in both low and high density gypsy moth populations. My study focused on the interactions between E. maimaiga and LdNPV. Laboratory bioassays in which I inoculated gypsy moth larvae with LdNPV and E. maimaiga at the same time indicated that the majority of dually inoculated larvae die from E. maimaiga because of the shorter incubation period of E. maimaiga (5-7 days) compared to LdNPV (14 days) at 20$\sp\circ$C. When the larvae were inoculated with E. maimaiga, 10 days after LdNPV inoculation, there was an apparent synergistic effect of E. maimaiga with LdNPV. Dually inoculated larvae died producing LdNPV propagules, 1-2 days earlier than the larvae inoculated with LdNPV alone. Small-scale field experiments conducted in mesh-bags showed that artificial rainfall increases the E. maimaiga transmission. In a naturally occurring, moderate density gypsy moth population, I found that the LdNPV infection level was little affected by the presence of E. maimaiga. Host heterogeneity is suspected as one of the factors leading non-linear LdNPV transmissions. I showed that the host heterogeneity cannot explain the E. maimaiga epizootic observed in low density populations. I experimentally demonstrated this by comparing the E. maimaiga infection rates in feral (experienced the E. maimaiga/LdNPV epizootic in their parental generations) and laboratory reared (with no epizootic experience) larvae. This is probably due to the short period to which the North American gypsy moths have been exposed to E. maimaiga, so these gypsy moths have not had chance to develop resistance against E. maimaiga.

The biology and behavioral ecology of Trichogramma ostriniae, an introduced egg parasitoid of Ostrinia nubilalis and other lepidopteran species were studied in the laboratory and under field conditions. The inter- and intra-specific discrimination, competition, and the effectiveness of T. ostrinia and T. nubilale were also investigated. For T. ostriniae to complete its life cycle, it took 6.7 days at 33$\sp\circ$C and 20 days at 17$\sp\circ$C. Comparison of several theoretic models indicated that a transformed day-degree model and the Hilbert-Logan model were better for predicting the development of this parasitiod. The wasps reared on O. furnacalis by the seventh generation and at 27$\sp\circ$C had a lower level of parasitism than wasps from other generations and at other temperatures. The differences among generations for the time female wasps spent drumming host eggs did not show any host and generation related trend. European corn borer egg parasitism was positively correlated with egg density. Female T. ostriniae might exhibit the Type II or Type III functional response depending on the temperature. The field data suggested a Type II functional response when data were pooled for all replicates. The effects of weather, plant size, and distribution of egg masses on egg parasitism by the wasp were studied in a sweet corn field. Logistic regression analyses indicated that percentage of eggs parasitized was negatively related to an increase in leaf area and distance of eggs from release point. Eggs on leaves in the upper third of a corn plant received much less parasitism than those on the middle and lower third. Temperature as well as the length of exposure of egg to wasps also affected the level of egg parasitism. Laboratory test on the cross breeding between T. ostriniae and T. nubilale indicated no successful hybridization. The results of the inter- and intra-specific discrimination and competition between the two species revealed that only female T. ostriniae discriminated eggs parasitized by females of the same species. When both species oviposited the same egg, T. ostriniae was most likely to be able to complete development. The level of egg parasitism by releasing T. ostriniae alone was found to be 15% higher than that by releasing T. nubilale alone, and 20% higher than by releasing a combination of the two species. Further analyses using the logistic regression model for independent and correlated data indicated T. ostriniae to be more efficient at discovering host egg masses than T. nubilale. Mutual interference between the two species was the main factor for the lower level of egg parasitism when the two species were released together. The results suggest that T. ostriniae is the better candidate for augmentative releases for control of the European corn borer, and the two species should not be released into a corn field at the same time.

The study presented in this dissertation concerns the epidemiology of eastern equine encephalitis (EEE) in Massachusetts. Human serosurveys were conducted in case neighborhoods to determine the inapparent infection rate and to test the hypothesis of focality of EEE virus transmission. An inapparent transmission rate of up to 1.85% was observed at epidemic foci. Focality of transmission was supported by the identification of an inapparent infection less than 10 meters from a 1990 case site. Putative epidemic EEE virus vector populations were compared at 15 case sites in Massachusetts. Carbon dioxide baited American Biophysics Corporation (ABC) light traps were used for trapping mosquitoes to estimate biting risk. These population data along with biological and behavioral data from other studies suggest that Coquillettidia perturbans (Walker), Aedes canadensis (Theobald), and Culex salinavius (Coquillett) may be more important vectors than the other potential vectors for EEE virus in Massachusetts, Aedes vexans (Meigen), Anopheles punctipennis (Say) and Anopheles quadrimaculatus (Say). Stepwise linear regression models were constructed from remotely sensed landscape data and Geographic Information System (GIS) Technology. Wetlands accounted for up to 72.5% of the observed variation in the host seeking populations of Ae. canadensis, Ae. vexans, and Culesita melanura. Stepwise linear regressions also demonstrated deciduous wetlands to be the specific wetland category contributing to the major class models. Pesticide targeting of deciduous (or coniferous) wetlands may be an effective way of controlling the abundance of Cs. melanura, Ae. canadensis and Ae. vexans. The effect of EEE virus on survivorship was determined for three possible epidemic vectors: Aedes albopictus, An. quadrimaculatus and Cq. perturbans. Female mosquitoes of these three species were exposed to EEE virus through infected blood meals and compared to uninfected controls for differential survival. Additionally, survival of Cq. perturbans and An. quadrimaculatus mosquitoes intrathoracically inoculated with EEE virus was compared to controls receiving diluent inoculations. It was shown that neither Ae. albopictus nor An. quadrimaculatus experienced reduced survivorship. Reduced survival was observed among Cq. perturbans orally infected with EEE virus. Damage to the midgut epithelium by EEE virus may be the cause of the increased mortality in this vector.