Field bioassays of cerambycid pheromones reveal widespread parsimony of pheromone structures, enhancement by host plant volatiles, and antagonism by components from heterospecifics

Recent research has revealed extensive pheromonal parsimony within the large beetle family Cerambycidae, with closely related species producing the same or very similar pheromone components. This article summarizes research that evaluated attraction of cerambycids to individual pheromone components, blends of pheromone components, and combinations of pheromones with host plant volatiles. Field bioassays were carried out, in collaboration with the Pennsylvania Department of Agriculture and the USDA Cooperative Agricultural Pest Survey program, in 10–25 counties of Pennsylvania over 3 years. A total of 15,438 cerambycids of 134 species were captured, including two exotic species. Semiochemical lures attracted significant numbers of beetles in species of the subfamilies Cerambycinae, Lamiinae, and Spondylidinae, but were not attractive to species in the Lepturinae, Parandrinae, and Prioninae. These experiments reconfirmed the behavioral roles of semiochemicals for a number of species that have been studied previously, and yielded new information about semiochemistry of several species. The host plant volatile α-pinene enhanced attraction of species that were conifer specialists, whereas ethanol enhanced attraction of some species of hardwood specialists. The data suggest that species which share dominant pheromone components avoid cross attraction by differing in seasonal activity period, and by antagonistic effects of minor pheromone components on attraction of heterospecifics. This study further supports the concept that with careful choice of components, multiple pheromones can be deployed as single blends, and paired with host plant volatiles, to maximize the number and taxonomic diversity of cerambycid beetles that are attracted to a single lure, so that the number of different lures that must be deployed can be minimized.     

Plant volatiles are behavioral cues for adult females of the gall wasp Antistrophus rufus

Summary. The purpose of this study was to identify plant volatiles that provide host location cues for adult females of the gall wasp Antistrophus rufus Gillette (Hymenoptera: Cynipidae). Larvae of this species inhabit flowering stems of the prairie perennial Silphium laciniatum L. (Asteraceae). Adult females responded to volatile compounds emitted by stems of S. laciniatum in field olfactometer bioassays. Plant volatiles were monoterpenes, including, in descending order of abundance, racemic - and -pinene (~50% + enantiomer for both), (+)-limonene, (–)-camphene, and -myrcene. In laboratory bioassays, females responded to aeration extracts of plant stems, the full blend of synthetic monoterpenes, and the four-component blend of -pinene, -pinene, (+)-limonene, and (–)-camphene. This monoterpene blend apparently serves as an olfactory cue for host plant location for female A. rufus and is the first such cue to be reported for a cynipid gall wasp. Species-specific ratios of plant monoterpenes may provide cues for gall wasp females to distinguish between plant species and choose appropriate hosts for oviposition. The olfactometer and bioassay techniques developed for this research may be useful for field bioassays of other types of minute arthropods.