Plant-feeding insects are the most species-rich group on the planet today. Models have been proposed to explain this diversity, but few use the fossil record to evaluate hypotheses. I conduct studies in modern systems to examine (1) taphonomic biases in insect preservation and how this may affect our understanding of insect diversity trends through time and (2) patterns of herbivory in modern ecosystems to improve the comparability of fossil and modern datasets. I then use the Cenozoic fossil record to examine the history of ecological associations between insects and plants and how these interactions respond to environmental change. I conducted an actualistic study on the preservation of beetles in Willcox Playa, an ephemeral lake in SE Arizona. I compared the insect death assemblage in shoreline sediments to the living beetle assemblage. The sediments captured 56% of the live-collected beetle families, and 28% of the live-collected beetle genera. The relative abundances of living beetles were not reflected in the death assemblage. Beetle diet, feeding habitat, and size influenced the composition of the death assemblage. Necrophagous, ground-dwelling and smaller beetles were over-represented in the death assemblage. Such biases should be considered in insect paleoepology and in studies of diversity change. Annual variation in herbivory was compared within and between two lowland neotropical forests Costa Rica. Herbivory did not vary significantly within sites between years, but was significantly different: between sites. Modern herbivory data collected with discrete sampling techniques is compartable to herbivory data from fossil forests. Herbivory data from one-time collections of leaf litter are most suitable for comparison with fossil herbivory. I compared herbivory between two Eocene floras and between the Eocene floras and six modern floras. A decline in levels of herbivory corresponds with a decline in temperature from the middle to the late Eocene. Fossil herbivore damage was significantly lower than modern herbivore damage. This pattern may result from taphonomic bias, environmental differences between the fossil and modern sites or evolutionary change.

This work focused on how visual and olfactory cue use by insects affect tritrophic interactions among the Arizona walnut, Juglans major (Juglandaceae), the fly Rhagoletis juglandis (Diptera: Tephritidae), whose larvae feed on the husk surrounding walnut fruits, and the parasitic wasp Biosteres juglandis (Hymenoptera: Braconidae: Opiinae) which oviposits in the fly larvae. The foraging behavior of female Biosteres juglandis was studied in the field and greenhouse, with specific attention paid to their use of visual and olfactory cues produced by walnut fruits harboring R. juglandis larvae. Field work demonstrated that wasps are successful in locating fruits infested with host larvae interspersed among uninfested fruits, and that they use fruit phenological traits (i.e. stage of rot) to do so. The method by which females appear to choose fruits in the field is functional, provided there are high host infestation levels. In greenhouse assays, fruit damage (apart from larval presence) was specifically identified as an important cue affecting wasp fruit choice. Wasps are also able to orient to infested fruits using only one type of cue, either olfactory or visual. Preliminary data from a pilot analysis of volatile compounds associated with infested, uninfested, and artificially damaged walnuts indicated that visual cues were more important than olfactory cues to free-foraging wasps. Rhagoletis juglandis adult females visit walnut fruits for oviposition, while adult males visit them to obtain matings. The effect of fruit color pattern on the behavior of male and female flies both inexperienced and experienced with real ripe walnuts was studied in the greenhouse. Overall, both sexes of flies exhibited a landing preference for plastic fruit models that appear ripe and uninfested, over models that appear infested. The behavior of both sexes may be driven by females who are attempting to provide offspring with the most possible food resources. Finally, the growth and germination of Arizona walnut seeds was followed to determine whether either was affected by infestation of the husk by R. juglandis. Although infested fruits were more likely to fall off a tree sooner, this did not affect the size of a walnut or its ability to germinate.

The diversity of many groups of organisms is related to the evolution of features that contribute to rapid radiations. This project reconstructed the phylogeny of carabid beetles in the subfamily Harpalinae, a speciose group of terrestrial predators. The phylogenetic inference focused on the sister group relationships, the monophyly of the subfamily and the tribal relationships within harpalines. Molecular sequence data, primarily from 28S ribosomal DNA and the wingless gene, were collected from more than 200 carabid beetles. Parsimony, minimum evolution distance, maximum likelihood, and Bayesian phylogenetic analysis methods were used to reconstruct the phylogeny of harpalines. Brachinine bombardier beetles and austral psydrines were found to be closely related to the harpaline clade. Within harpalines, zuphiites formed a clear clade as did pseudomorphines + graphipterines + orthogoniines. However the lebiomorph assemblage and the tribe Lebiini were not monophyletic. With the use of harpaline phylogenetic hypotheses, the evolution of the arboreal lifestyle was elucidated within the subfamily, including the rate and number of origins and losses of arboreality. Correlated evolution of several morphological characters and habitat was explored. Significant correlation of adhesive subtarsal setae and bilobed fourth tarsomeres on carabid legs were found with arboreality and may be arboreal adaptations, while long legs and long elytra are probably not associated with arboreality. The relationship of other morphological characters with arboreality is not clear. Harpalines may have been part of a rapid radiation of species diversity, where many lineages invaded new ecological niches and evolved novel morphological features to become adapted to their environment.

In this dissertation I employ a comparative gene expression approach to address the evolution of butterfly wing pattern formation at several levels, with emphasis on early pattern determination and pigment gene regulation during late development. Expression analysis of the receptor molecule Notch suggested previously unknown roles for Notch signaling in butterfly wing patterning. Notch upregulation was found to precede the activation of the transcription factor Distal-less during early eyespot color pattern determination. A phylogenetic comparison of expression time series from multiple moth and butterfly species suggested that changes in a Notch/Distal-less temporal pattern formation process were associated with the gain and loss of both eyespot and midline color patterns during wing pattern evolution. Additionally, Notch expression was found to occur in a grid-like pattern in the butterfly wing epithelium shortly after pupation. This observation, together with previous expression and simulation studies, support a Notch-mediated lateral inhibition model of wing scale organization. Tryptophan-derived ommochrome pigments are a derived feature of nymphalid butterfly wings. I found that multiple genes in the ommochrome biosynthetic pathway were expressed in the wings of selected nymphalid butterflies. Additionally, transcriptional regulation of genes encoding the ommochrome synthesis enzymes vermilion and cinnabar was found to be temporally and spatially associated with the polymorphism and development of forewing band patterns in the mimetic butterfly Heliconius erato. These findings provide evidence that changes in ommochrome gene regulation underlie the evolution and development of major nymphalid wing pattern elements.

I examined resistance to cold temperature in seven Drosophila species from different habitats to determine the lower limits of cold tolerance. Three separate tests were administered to measure the: (1) response to a cold-shock exposure; (2) extent to which a short-term survival strategy, rapid cold hardening, was utilized by each species; and (3) degree to which each species would respond to a prolonged exposure at 0°C. As expected, the temperate-montane species, D. pseudoobscura, was the most cold-tolerant, whereas the least cold-tolerant was the tropical species, D. paulistorum. The two cosmopolitan species, D. hydei and D. melanogaster, and the three Sonoran Desert endemic species, D. mojavensis, D. nigrospiracula, and D. mettleri, demonstrated intermediate levels of cold-tolerance. Of the five species tested for rapid cold hardening, all exhibited the response, including the tropical representative. The results for the 0°C test paralleled the results of the cold shock test. The desert species tested proved surprisingly cold-tolerant, especially D. mojavensis.

Two factors affecting the mutualism between Myrmecocystus mendax and Publilia modesta are investigated. These factors are the seasonal time frame during which the mutualism is maintained and the behavior of individual workers tending membracid aggregations. Results of this study show that Publilia modesta makes seasonal migrations via flight, makes use of a conifer as a long term host, mates on a substate distant from a suitable oviposition host, and changes color with the onset of ovarian development many months after metamorphosis. Membracid-tending Myrmecocystus mendax comprise a behaviorally distinct subcaste and behave in a manner consistent with optimal foraging theory by maintaining both site and resource fidelity.

Blood fed Culex quinquefasciatus were collected from residential and wetland sites in Tucson, Arizona for three years using CDC gravid traps. An ELISA distinguishing human, bird, dog, cat, and rabbit blood meals was used. In residential areas, approximately 47% of all identified blood meals were from humans, with fewer blood meals from bird, dog, cat, and rabbit. At Sweetwater Wetland, humans were also the most common host, with 11 (41%) identified blood meals. Birds were the hosts of 19% blood meals. Ten (seven residential, three wetland) mosquitoes were identified to have blood from both bird and human hosts. Since the transmission of West Nile Virus to humans is dependent on mosquitoes feeding both on birds and humans, this finding is particularly relevant. These data only describe the feeding choices of the mosquitoes collected from a limited number of sites in Tucson, and therefore, may not reflect feeding preferences more generally.

<p> As herbivorous insects choose where to lay their eggs, maximizing larval performance (optimal oviposition) may be at odds with adult foraging (optimal foraging). Aspen leaf miners (<i>Phyllocnistis populiella</i>; ALM) may choose between leaves with or without extrafloral nectaries (EFNs) as oviposition sites on quaking aspen (<i>Populus tremuloides</i> Michx.). Reduced ALM mining on leaves with EFNs may be linked to predators that defend leaves and feed at EFNs, and to increased concentrations of secondary leaf compounds. However, direct responses of adult ALM to EFN expression may also explain differences in ALM mining among leaves with and without EFNs. ALM might be less likely to oviposit on leaves with EFNs because these leaves provide poor conditions for larval development. With choice experiments and surveys of ALM oviposition, we examined oviposition site preference in relation to EFN expression. In choice experiments and field surveys adults preferred to oviposit on leaves without EFNs. Increased oviposition was also observed on shoots with high EFN frequencies, suggesting a combination of optimal foraging and optimal oviposition, and a role of EFNs at scales above the leaf level. Higher predation on leaves with EFNs likely exerts selective pressure for the observed ALM oviposition preference for non-EFN leaves.</p>

<p> Two field trials were conducted to determine the impact of water management on the efficacy of insecticide seed treatments against rice water weevil, <i> Lissorhoptrus oryzophilus</i> Kuschel, in rice at the Delta Research and Extension Center during 2011 and 2012. The performance of thiamethoxam, chlorantraniliprole, and clothianidin was evaluated when the permanent flood was established at different timings (6 and 8 weeks after planting) and the effect of flush number (0, 1, or 2) on seed treatment performance was evaluated. Seed treatment efficacy was not impacted by delayed flooding, but 2 flushes reduced efficacy of some seed treatments. </p><p> Experiments were also conducted to determine the impact of reduced seeding rates found in hybrid rice production on the efficacy of insecticide seed treatments targeting rice water weevil. Efficacy was similar when comparing currently labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin with higher rates of these products.</p>

The problem of malaria in the South, and in other parts of the United States as well, has demanded a considerable amount of research. The greater part of this work has been concerned with the control of the disease by the eradication of the anopheline mosquitoes, and much of such work recently has dealt with the ecological aspects of the problem. Such factors as temperature, humidity, larval food, plant associates, hydrogen-ion concentration of the water of larval breeding places, and many others have been considered. The effects of these various factors on the life and habits of the mosquitoes usually differ for the various species and often differ for a single species in different parts of its range. Since the life of an animal is never entirely governed by a single factor, but by a complex combination of interrelated factors, each area studied offers to some extent a condition peculiar to the location. In the following pages an attempt will be made, after the plotting of fluctuations in the seasonal abundance of the one common Anopheles of the region, Anopheles quadrimaculatus Say, to evaluate the various ecological factors involved in producing these fluctuations. It will be shown that the influence of some of these factors is of very local nature; that is, certain factors may operate in quite different manners and may be of decidedly different importance in a locality where a bayou is the main source of emerging mosquitoes, on the one hand, and in a nearby locality where flooded rice fields are the main source. This survey covered the period of time from March 1932 to January 1934. The area studied included the southern part of the city of Houston and immediate vicinity outside the city limits, and also a rice farming district 15 miles to the west of the city.