Trapping of Retrachydes thoracicus thoracicus (Olivier) and Other Neotropical Cerambycid Beetles in Pheromone- and Kairomone-Baited Traps.

The subfamily Cerambycinae, one of the most diverse in longhorn beetles, is well known for its remarkable chemical parsimony in male-emitted pheromones. Conserved shared structural motifs have been reported in numerous species, sometimes working in combination with plant volatile kairomones. Among other compounds, the most ubiquitous male pheromone in cerambycine species is 3-hydroxyhexan-2-one. We conducted field trials using intercept traps baited with 3-hydroxyhexan-2-one and observed abundant captures of several Neotropical cerambycine species. These were Retrachydes thoracicus thoracicus (Olivier), Megacyllene acuta (Germar), Compsocerus violaceus (White), and Cotyclytus curvatus (Germar) in high numbers, as well as Chydarteres striatus striatus (Fabricius) and Odontocroton flavicauda (Bates) in smaller numbers. When ethanol was added to the traps, a remarkable increase in the attractiveness of 3-hydroxyhexan-2-one was observed for R. thoracicus thoracicus and M. acuta. Adding ethanol also resulted in the capture of Chrysoprasis aurigena (Germar). Finally, incidental catches in pheromone-baited traps of Trachelissa maculicollis (Audinet-Serville), Neoclytus pusillus (Laporte & Gory), Achryson unicolor (Bruch, 1908) and Achryson surinamum (Linnaeus), Megacyllene mellyi (Chevrolat) and Thelgetra adustus (Burmeister) were also observed. Pheromone chemistry has been reported for C. curvatus, M. acuta and N. pusillus, all three producing 3-hydroxyhexan-2-one, and for C. aurigena and A. surinamum, which produce other compounds. Our findings suggest that the captured species probably produce 3-hydroxyhexan-2-one for their pheromone communication system. Alternatively, they might be "eavesdropping" on the pheromones of other cerambycine species. The probable synergistic effect of ethanol is likely explained from its kairomonal role as a volatile cue for plant stress or ripeness.