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The study of insect semiochemistry has vast implications for pest management, conservation efforts, and the evolution of insects. Insect semiochemicals, or chemicals emitted by insects to communicate with conspecific individuals or other organisms, are increasingly used for integrated pest management, have been instrumental in eradicating economically important pests, can be used to assess the health of ecosystems, and can be a tool in elucidating evolutionary and taxonomic relationships. For these and other reasons, it is important to study the semiochemistry of insects.Semiochemicals used in long-distance communication are volatile, thus, the headspace odors released by insects or host plants can be collected and analyzed. Using both well-established and recently developed chemistry, my goal was to identify and prepare synthetic standards of new semiochemicals. These chemicals have been/will be used in field experiments to unambiguously verify the structures and elucidate the functions of these semiochemicals. Insect semiochemicals often contain stereocenters, so in the case that mixtures of stereoisomers are ineffective in field experiments, synthesis of enantioenriched or enantiopure material must be conducted.The following chapters describe the analysis of several plant- and insect-produced semiochemicals. The introductory chapter reviews the importance of structure and chirality in insect olfaction and provides an overview of the study of semiochemicals, with several interwoven examples from the natural world. In the second chapter, I report the identification of a novel diterpene hydrocarbon that attracts the invasive stink bug Bagrada hilaris (Hemiptera: Pentatomidae). This stink bug is an important pest of Brassica crops such as broccoli, kale, and cauliflower. With volatile extracts of the headspace odors from cauliflower Brassica oleracea var. botrytis seedlings, the structure and absolute configuration of the tricyclic diterpene, ultimately named brassicadiene, were determined.In the remaining chapters, I describe the identification and synthesis of a sex-attractant pheromone ((1S,3S,4R)-3-hydroxy-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one) of the “unlighted” winter firefly Ellychnia corrusca (Coleoptera: Lampyridae), and aggregation-sex pheromones for several longhorn beetles (Coleoptera: Cerambycidae). Specifically, the identifications and syntheses of the pheromone (p-mentha-1,3-diel-9-ol) shared by the Eurasian longhorn beetle Aromia moschata and the North American longhorn beetle Holopleura marginata, and the likely pheromone ((4R,6S,7E,9E)-4,6,8-trimethylundeca-7,9-dien-3-one) shared by the North American longhorn beetle Graphisurus fasciatus and South American longhorn beetle Eutrypanus dorsalis, are described.

Longhorn beetles (Cerambycidae) are a diverse family of beetles that can cause considerable damage as forest pests and vectors of pathogens, as well as being important components of forest food webs and ecosystem functionality. In recent years, numerous cerambycid pheromones have been identified, revealing some broad general patterns in functionality in terms of sex or aggregation-sex pheromones in different subfamilies and different types of compounds characterizing the pheromones of various cerambycid taxa. Here, we describe the identification of the aggregation-sex pheromones of the Eurasian longhorn beetle Aromia moschata moschata (L.) (Cerambycinae; tribe Callichromatini) and the North American species Holopleura marginata LeConte (Cerambycinae; Holopleurini), as part of an ongoing effort to extend the taxonomic coverage of identified cerambycid pheromones and to expand the prospects for cerambycid monitoring into the study of biodiversity and ecosystem services. Both species were found to use the novel pheromone compound p-mentha-1,3-dien-9-ol, which also attracted significant numbers of the longhorn beetle Xestoleptura crassipes (LeConte) (Lepturinae; Lepturini) in trials in California. p-Mentha-1,3-dien-9-ol represents a class of pheromone compounds novel to both tribes (Callichromatini and Holopleurini), further increasing the chemical space of identified pheromones within the subfamily Cerambycinae. This compound is also noteworthy because it represents an entirely different chemical class of pheromones than the monoepoxide (E)-2-cis-6,7-epoxynonenal, previously reported as an aggregation-sex pheromone for the invasive Asian congener Aromia bungii (Faldermann).