The wide-spread use of insecticides has contributed to the rapid decline of insect diversity and abundance. In light of recent guidance from international and governmental organizations, other non-chemical control methods are necessary to control insect pest populations. In my study, I used occupancy modeling techniques and found that environmental variables could predict the presence of Rhaphidophoridae, in Hidalgo, Mexico. The results showed that variables associated with forested habitats increase the probability of Rhaphidophoridae detection, and higher elevation increases the probability of Rhaphidophoridae occupancy. Understanding the specific habitat variables associated with human detection and occupancy of Rhaphidophoridae give people the ability to utilize the Integrative Pest Management (IPM) strategy of cultural control to prevent Rhaphidophoridae pest populations in my study region.

Pollinator populations globally have declined at concerning rates in recent years, which is problematic given that roughly a third of all food production depends on them. Managed honey bee colony losses in particular have alarmed beekeepers and scientists, especially in the United States. Widespread agrochemical use has been implicated as one of the major causes of these colony losses. While the lethal effects of agrochemicals often receive the most attention, sublethal effects can occur at lower doses and can substantially weaken colonies over time. Impaired associative learning ability is a sublethal effect of a number of agrochemicals, and is particularly concerning, as it may hinder the abilities of bees to forage for food or find their way back to the colony. Here, I focus on the fungicide Pristine® (active ingredients: 25.2% boscalid, 12.8% pyraclostrobin), which is sprayed on honey bee-pollinated crops during bloom and is known to poison bee mitochondria at ppm levels. First, I show that Pristine® impairs performance on an associative learning assay in the laboratory. Next, I show that Pristine® alters carbohydrate absorption in honey bees, providing a possible mechanism underlying this impaired learning performance. Finally, I demonstrate that Pristine® interacts with high temperatures to induce homing failure in exposed bees. My results raise concerns that this common fungicide may not be safe for pollinators and will be relevant to policymakers as they make decisions surrounding the regulation of fungicide use in agriculture.

Understanding how and why animals choose what to eat is one of the fundamental goals of nutritional and behavioral biology. This question can be scaled to animals that live in social groups, including eusocial insects. One of the factors that plays an important role in foraging decisions is the prevalence of specific nutrients and their relative balance. This dissertation explores the role of relative nutrient content in the food selection decisions of a species that is eusocial and also agricultural, the desert leafcutter ant Acromyrmex versicolor. A dietary choice assay, in which the relative amount of protein and carbohydrates in the available diets was varied, demonstrated that A. versicolor colonies regulate relative collection of protein and carbohydrates. Tracking the foraging behavior of individual workers revelaed that foragers vary in their relative collection of experimental diets and in their foraging frequency, but that there is no relationship between these key factors of foraging behavior. The high proportion of carbohydrates preferred by lab colonies suggests that they forage to nutritionally support the fungus rather than brood and workers. To test this, the relative amounts of 1) fungus, and 2) brood (larvae) was manipulated and foraging response was measured. Changing the amount of brood had no effect on foraging. Although decreasing the size of fungus gardens did not change relative P:C collection, it produced significant increases in caloric intake, supporting the assertion that the fungus is the main driver of colony nutrient regulation. The nutritional content of naturally harvested forage material collected from field colonies was measured, as was recruitment to experimental diets with varying relative macronutrient content. Field results confirmed a strong colony preference for high carbohydrate diets. They also indicated that this species may, at times, be limited in its ability to collect sufficiently high levels of carbohydrates to meet optimal intake. This dissertation provides important insights about fundamental aspects of leafcutter ant biology and extends our understanding of the role of relative nutrient content in foraging decisions to systems that span multiple trophic levels.

The flexibility and robustness of social insect colonies, when they cope with challenges as integrated units, raise many questions, such as how hundreds and thousands of individual local responses are coordinated without a central controlling process. Answering such questions requires: 1. Quantifiable collective responses of colonies under specific scenarios; 2. Decomposability of the collective colony-level response into individual responses; and 3. Mechanisms to integrate the colony- and individual-level responses. In the first part of my dissertation, I explore coordinated collective responses of colonies in during the alarm response to an alarmed nestmate (chapter 2&3). I develop a machine-learning approach to quantitatively estimate the collective and individual alarm response (chapter 2). Using this methodology, I demonstrate that colony alarm responses to the introduction of alarmed nestmates can be decomposed into immediately cascading, followed by variable dampening processes. Each of those processes are found to be modulated by variation in individual alarm responsiveness, as measured by alarm response threshold and persistence of alarm behavior. This variation is modulated in turn by environmental context, in particular with task-related social context (chapter 3). In the second part of my dissertation, I examine the mechanisms responsible for colonial changes in metabolic rate during ontogeny. Prior studies have found that larger ant colonies (as for larger organisms) have lower mass-specific metabolic rates, but the mechanisms remain unclear. In a 3.5-year study on 25 colonies, metabolic rates of colonies and colony components were measured during ontogeny (chapter 4). The scaling of metabolic rate during ontogeny was fit better by segmented regression or quadratic regression models than simple linear regression models, showing that colonies do not follow a universal power-law of metabolism during the ontogenetic development. Furthermore, I showed that the scaling of colonial metabolic rates can be primarily explained by changes in the ratio of brood to adult workers, which nonlinearly affects colonial metabolic rates. At high ratios of brood to workers, colony metabolic rates are low because the metabolic rate of larvae and pupae are much lower than adult workers. However, the high colony metabolic rates were observed in colonies with moderate brood: adult ratios, because higher ratios cause adult workers to be more active and have higher metabolic rates, presumably due to the extra work required to feed more brood.

The global spread of the Aedes aegypti mosquito, a competent disease vector, is occurring at an alarming pace. These invasive mosquitos have spread to latitudes once thought inaccessible due to thermal and hydric limitations, including Maricopa County, AZ, where strong increases in population size has occurred over the last decade. The Aedes aegypti in Maricopa County follow a highly seasonal pattern with populations all but disappearing each winter, only to return and build exponentially though the summer and fall. Maricopa County’s winters are relatively mild, which raises the question of whether further global climate change will warm conditions enough to create a broadened seasonal breeding period, or worse yet, year-round mosquito activity within desert southwest cities. This dissertation focuses on exploring the possible seasonal constraints on the egg, larva, and adult life stages of the Aedes aegypti mosquito within a suburban desert ecosystem. I explored whether climatic warming would raise temperatures enough to enable survival and development of these animals during the winter offseason. I determined that larval growth and adult flight are constrained by ambient winter temperatures in Maricopa County, explaining the currently observed winter crash in populations. However, warming by only a few degrees Centigrade could enable successful larval growth and development, as well as adult flight, even during the coldest desert months. I found that load and temperature interact to determine the flight cost of mosquitos, which can very up to six-fold, with higher temperatures likely increasing their flight performance but decreasing their distance capacities and increasing their need for fuel. Aedes aegypti likely primarily overwinters as eggs. However, I showed that the vast majority of Aedes aegypti eggs die overwinter in Maricopa County. By manipulating humidity in eggs exposed to ambient air temperatures, I showed that desiccation, not cold temperatures, is the limiting factor in long-term survival of Aedes aegypti eggs. Together, my data suggests that humid, urban microhabitats may be essential for enabling overwinter egg survival in Maricopa County, providing a potential important pathway toward control of this disease vector.