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Mosquito phytophagy is a critical component of mosquito biology, contributing to their survival, flight activity and reproductive output and thus fueling their role as deadly vectors of disease. To alleviate the issues faced by current control methods, such as increased insecticide resistance and environmental damage, novel control strategies have emerged that exploit the mosquito's biological need to feed on sugar. However, an improved understanding of sugar feeding behavior is needed to better optimize these strategies. Here, we determined the prevalence of mosquito sugar feeding on ornamental plants and wildflowers by using DNA barcoding on mosquitoes captured in residential Blacksburg, VA, and identified their preferences for commonly planted flower species. Based on this information, we then confirmed the rate of sugar feeding on the attractive flower goldenrod (Solidago spp.) in the wild and explored its attractive qualities with the intent of developing a novel, ecologically friendly attractant. Similarly, we observed the sugar feeding behavior of invasive species Aedes japonicus on the toxic native flower fly poison and assessed its suitability as a naturally sourced attractant and toxin for use in attractive toxic sugar baits. Finally, we compared the morphology, metabolism and life history traits of mosquito species with unique host preferences. This work expands our knowledge on mosquito phytophagy and contributes to the development of new, highly needed control strategies. / Doctor of Philosophy / Mosquitoes are considered by many to be a blood-feeding nuisance and a vector of disease. While it is true that the females of several species need blood to develop their eggs and transmit disease-causing pathogens through blood feeding, mosquitoes need to frequently feed on plant-derived sugars to survive in the wild. In fact, male mosquitoes feed exclusively on sugar and both sexes use sugar as an energy source for flight. Because sugar feeding is such a critical component of mosquito biology, many novel disease vector control strategies have recently emerged that exploit this behavior, making it important to study. However, there is much that remains to be understood about their plant preferences and how they find these preferred plants in the wild. Here, we used new molecular techniques to determine what plant species mosquitoes commonly feed on in residential areas of Blacksburg, VA. We then explored the attractive qualities of goldenrod, a plant fed on frequently by mosquitoes in Montgomery County, VA. We also examined whether an invasive species, Aedes japonicus, can feed on the native toxic flower fly poison and analyzed the effect of sugar concentration on the metabolism, survival and egg-laying rate of two important invasive disease vectors: Aedes aegypti and Culex quinquefasciatus. The results found here improve our understanding of mosquito sugar feeding and have applications for the development of new disease control techniques.

Mosquitoes, by transmitting vector-borne diseases through their saliva, impact nearly half of the world's population. Mosquito survival is dependent on their sense of smell, or olfaction, which allows a mosquito to differentiate between plant nectar, required for metabolic processes, and host odors, which will help them navigate towards hosts, source of the blood required for producing eggs. Mosquitoes interpret and respond to chemical volatiles very differently depending on their environment (temperature, humidity, time of day, etc.) and species-specific host preferences (humans, mammals, etc.). However, the impact of ecological factors on mosquito prevalence, sugar-feeding, and host seeking is relatively unknown. In an attempt to address this knowledge gap, we first investigate how several ecological factors (i.e., temporal, seasonal, and topographical) affect mosquito sugar feeding and population dynamics. Second, we focused on the anthropophilic mosquito species Aedes aegypti to investigate the role of plant associated compounds in host-seeking behavior, such as those which are commonly found in personal care products (i.e., body washes). Our results demonstrate that several ecological factors alter mosquito prevalence and behavior, including both sugar and host seeking behaviors. We anticipate these results to be a starting point for mosquito control strategies that depend not only on olfactory perception of plant odors, but also on the ecological and species-specific characteristics which shape the dynamics of vector-borne diseases. / Master of Science in Life Sciences / Most female mosquitoes must feed on a blood source in order to produce eggs, but in doing this they can transmit viruses and pathogens between hosts through their saliva, which are contracted by 700,000 people per year. In order to survive and fly to locate these host sources, both female and male mosquitoes require sugar and carbohydrates present in plant nectar. Mosquito identification of nectar and blood sources is primarily dependent on their sense of smell, or olfaction, which allows a mosquito to identify and locate chemical odors. The interpretation of these chemical odors is context dependent on both the mosquitoes' hunger status, ideal host (human, mammal, bird, etc.) and environmental cues (temperature, humidity, time of day, etc.). It is relatively unknown how the combination of these biological and environmental factors influences mosquito survival and biting frequency. In order to better understand this relationship, we first investigated mosquito species' habitat preferences (i.e., urban and forested) and ecological factors (i.e., season, weather). Second, we focused on Aedes aegypti mosquitoes, which almost exclusively feed on humans in urban habitats, to investigate mosquito behavior in the presence of combined plant and human odors caused by the usage of fragrant personal care products that are scented with plant odors. Our results demonstrate that mosquito prevalence, host-seeking, and plant-seeking are highly dependent on chemical and ecological factors. We anticipate that this research has avenues for both improving mosquito control strategies and better understanding the ecological dynamics of vector-borne diseases.

Master of Science in Life Sciences / This thesis explores the feeding structures of insects, which have evolved over millennia to utilize a variety of dietary sources. It examines the mouthparts of insects feeding on plants, other bugs, or vertebrate blood, analyzing how these structures influence or limit their diet. Focusing particularly on mosquitoes, which are a significant public health threat due to their role as vectors of deadly diseases, we investigate the unique sexual dimorphism and diet, females' blood-feeding behaviors and the differences in the dual-pump feeding mechanisms of Aedes aegypti and Culex quinquefasciatus. Specifically, we investigated the effect of fluid viscosity on the sugar-feeding behavior and the pumping dynamics of males and females via force-feeding assays and electromyography (EMG) recording. Results showed varied pumping contraction frequencies among mosquito species and sexes that align with host feeding preferences. Furthermore, the study confirms that both species and sexes significantly influence sucrose intake, with Aedes aegypti females notably consuming more at higher concentrations, a trend not mirrored in Culex quinquefasciatus females. By studying the effects of fluid viscosity on feeding behavior and pumping dynamics, we inform computational models of the ingestion pumps that will help us gain insight into how the evolution of blood feeding.

The association of olfactory information with a resource is broadly known as olfactory-based associative learning. From an ecological perspective, associative learning can reduce search time for resources and fine tune responses to changing biotic and abiotic factors in a variable environment, which in mosquitoes has implications for pathogen transmission and vector control strategies. The purpose of this dissertation was to examine the ability for olfactory-based associative learning across the major life history domains of mosquitoes. Six different experiments comprise this dissertation. The first was to evaluate the response of mosquitoes following conditioning to 5, 10 or 50% sucrose concentrations with individual level mosquito conditioning and testing and introduction of statistical analysis with binary logistic regression. Mosquitoes did not respond in a dose dependent manner with respect to positive response to target odors following conditioning. This effect appears to be related to the mosquitoes' prior exposure to sugar as those exposed to 10% sucrose before conditioning did not prefer 50% sucrose but significantly fewer chose 5% sucrose. In an evaluation of host associated odors and second blood meal choice by females using a dual-choice olfactometer no significant effects were observed. The lack of significance may have been due to insufficient sample sizes, problems with odor collection or physiological state of mosquitoes. Effects of predatory mosquitofish on larval development and female oviposition choice were evaluated by rearing in separated habitats under three different treatments followed by an oviposition choice assay. Females did not prefer their natal habitat or avoid predators but chose substrate that had contained mosquitofish fed conspecific larvae. Mosquitofish affected larval development with acceleration in treatments with mosquitofish fed Tetramin® and delayed pupation in treatments with mosquitofish fed conspecific larvae. Mosquito memory length was evaluated by conditioning and testing at six time intervals from colony and field populations at two ages. Younger mosquitoes showed higher levels of positive response after conditioning at all time intervals except the longest (24h). Finally the olfactory-based associative learning ability of Anopheles cracens was evaluated. Significant evidence for learning was observed in males but not females at a memory length interval of 24h.

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