ULTRAMICROCHEMISTRY OF INSECT SEMIOCHEMICALS

Chemical ecology of the Insecta, comprises an invisible environment wh ere semiochemicals are the principal factors regulating the mating and host-selection of the one million or more species. Biologically effec tive concentrations of these semiochemicals range from 10(-10) to 10(- 3) mu g at the insect antennal receptors. These levels are virtually u ndetectable by conventional microchemistry, and can be measured only b y behavioral bioassay and by electrophysiology which are about 10,000 and 100-fold more sensitive than gas chromatography. Despite more than 40 years of study, the sex pheromones have been identified from only about 1300 species of insects (0.1%). The dearth of information about kairomones from host plants for phytophagous insects is even more asto nishing, and only about 400 plant species have been studied extensivel y (ca. 0.2%), and the odorant spectra characterized in only 10 importa nt crop plants. These odorants are chemically complex and their action as semiochemicals for insect herbivores, involves degrees of receptor specificity and synergism that are virtually unstudied. These lacunae in our knowledge of chemical ecology are fundamental to the study of ecology, behavior, and evolution of insects; but also are of vital imp ortance in applied entomology. There is much societal pressure to prog ress from broadcast application of insecticides, to specific and innov ative methods for insect control that are non-hazardous to human healt h and to environmental quality. Pest management strategies involving t he use of semiochemicals are essential to reach this goal. These inclu de monitoring insect populations vis-a-vis the economic threshold, the use of attracticide baits, and strategies for mating confusion and be havioral confusion of insect pest populations in row and orchard crops . The immensity of the semiochemical environments of plant and insect communities, the intellectual challenges for understanding ecology and evolution, and the immediate need for application to applied entomolo gy provide compelling reasons for enhanced study of the microchemistry of semiochemicals.