Chemical Ecology of Click Beetles (Coleoptera: Elateridae): First Identification of Sex Pheromones and Sex Attractants of North American Species
Click beetles (Coleoptera: Elateridae) are one of the most diverse and well recognized groups of beetles worldwide. Their diverse habitats and feeding behaviors result in a wide variety of ecological and economic roles for click beetles. Wireworms, the term applied to larvae of pestiferous species, form a devastating pest complex that threatens numerous vegetable and cereal crops on all continents. To date, the pheromonal signals that are crucial mediators of reproductive behaviors have not been exploited in integrated pest management (IPM) programs for North American elaterids. The utility of such pheromones for monitoring and control has been demonstrated for Eurasian elaterids, but prior to my thesis research, pheromones had not been identified for any North American species. Thus, my main goals were to jump-start elaterid pheromone research in North America, and to develop efficient protocols for collection, identification, and bioassay of elaterid pheromones.
The first portion of this work describes the identification of sex pheromones, sex attractants, and a hyperpheromone for two sympatric Cardiophorus species. Males were initially attracted to a known cerambycid beetle pheromone, fuscumol acetate. The actual pheromone was subsequently identified as (R)-methyl dihydrofarnesoate, which is structurally similar to fuscumol acetate. In a follow-up study, additional pheromone analogs were tested to further investigate the specificity of responses of males, resulting in the discovery of a compound which was >26 times as attractive as the natural pheromone of Cardiophorus edwardsi.
In the second section, I identified 13-tetradecenyl acetate as the sex pheromomone of Melanotus communis. Additional studies optimized lures for use in IPM programs for this agricultural pest. The final section describes identification of the sex pheromone of Idolus californicus, which started from a lead obtained from field screening of known pheromones of European species. Males were specifically attracted to neryl hexanoate, one of two compounds which were subsequently identified from females. The second compound was not attractive, although it elicited antennal responses from males, and also attracted males of a Dalopius species. The work presented here should lay the groundwork for future research into elaterid pheromones across the United States and worldwide.