Adults of both sexes of the cerambycid beetles Xylotrechus colonus (F.) and Sarosesthes fulminans (F.) were attracted to odors produced by male conspecifics in olfactometer bioassays. Analyses of headspace volatiles from adults revealed that male X. colonus produced a blend of (R)- and (S)-3-hydroxyhexan-2-one and (2 S,3 S)- and (2R,3R)-2,3-hexanediol, whereas male S. fulminans produced (R)-3-hydroxyhexan-2-one and (2 S,3R)-2,3-hexanediol. All of these compounds were absent in the headspace of females. Two field bioassays were conducted to confirm the biological activity of the synthesized pheromones: (1) enantiomerically enriched pheromone components were tested singly and in species-specific blends and (2) four-component mixture of racemic 3-hydroxyhexan-2-one plus racemic 2-hydroxyhexan-3-one and the four-component blend of the stereoisomers of 2,3-hexanediols were tested separately and as a combined eight-component blend. In these experiments, adult male and female X. colonus were captured in greatest numbers in traps baited with the reconstructed blend of components produced by males, although significant numbers were also captured in traps baited with (R)-3-hydroxyhexan-2-one alone or in blends with other compounds. Too few adult S. fulminans were captured for a statistical comparison among treatments, but all were caught in traps baited with lures containing (R)-3-hydroxyhexan-2-one. In addition to these two species, adults of two other species of cerambycid beetles, for which pheromones had previously been identified, were caught: Neoclytus a. acuminatus (F.) and its congener Neoclytus m. mucronatus (F.). Cross-attraction of beetles to pheromone blends of other species, and to individual pheromone components that are shared by two or more sympatric species, may facilitate location of larval hosts by species that compete for the same host species.

Many species of cerambycid beetles in the subfamily Cerambycinae are known to use male-produced pheromones composed of one or a few components such as 3-hydroxyalkan-2-ones and the related 2,3-alkanediols. Here, we show that this pheromone structure is characteristic of the cerambycine genus Neoclytus Thomson, based on laboratory and field studies of 10 species and subspecies. Males of seven taxa produced pheromones composed of (R)-3-hydroxyhexan-2-one as a single component, and the synthetic pheromone attracted adults of both sexes in field bioassays, including the eastern North American taxa Neoclytus caprea (Say), Neoclytus mucronatus mucronatus (F.), and Neoclytus scutellaris (Olivier), and the western taxa Neoclytus conjunctus (LeConte), Neoclytus irroratus (LeConte), and Neoclytus modestus modestus Fall. Males of the eastern Neoclytus acuminatus acuminatus (F.) and the western Neoclytus tenuiscriptus Fall produced (2S,3S)-2,3-hexanediol as their dominant or sole pheromone component. Preliminary data also revealed that males of the western Neoclytus balteatus LeConte produced a blend of (R)-3-hydroxyhexan-2-one and (2S,3S)-2,3-hexanediol but also (2S,3S)-2,3-octanediol as a minor component. The fact that the hydroxyketone-hexanediol structural motif is consistent among these North American species provides further evidence of the high degree of conservation of pheromone structures among species in the subfamily Cerambycinae.

Eusocial insects use cuticular hydrocarbons as components of pheromones that mediate social behaviours, such as caste and nestmate recognition, and regulation of reproduction. In ants such as Harpegnathos saltator, the queen produces a pheromone which suppresses the development of workers' ovaries and if she is removed, workers can transition to a reproductive state known as gamergate. Here we functionally characterize a subfamily of odorant receptors (Ors) with a nine-exon gene structure that have undergone a massive expansion in ants and other eusocial insects. We deorphanize 22 representative members and find they can detect cuticular hydrocarbons from different ant castes, with one (HsOr263) that responds strongly to gamergate extract and a candidate queen pheromone component. After systematic testing with a diverse panel of hydrocarbons, we find that most Harpegnathos saltator Ors are narrowly tuned, suggesting that several receptors must contribute to detection and discrimination of different cuticular hydrocarbons important in mediating eusocial behaviour.Cuticular hydrocarbons (CHC) mediate the interactions between individuals in eusocial insects, but the sensory receptors for CHCs are unclear. Here the authors show that in ants such as H. saltator, the 9-exon subfamily of odorant receptors (HsOrs) responds to CHCs, and ectopic expression of HsOrs in Drosophila neurons imparts responsiveness to CHCs.