Dendroctonus frontalis; HYMENOPTERAN-PARASITES; Roptrocerus xylophagorum & Spathius pallidus; Parasitoid responses to semiochemicals from plant hosts; PLANT-HOSTS; Pine trees; Semiochemicals from hosts, hymenopteran parasite responses; GEORGIA-USA; Fort Benning & Oconee National Forest; Semiochemicals from plant hosts, hymenopteran parasitoid responses Roptrocerus xylophagorum; Spathius pallidus; CHEMORECEPTION-; COLEOPTERAN-HOSTS; Dendroctonus frontalis; Parasitoid responses to semiochemicals from plant hosts; GEORGIA-USA; Fort Benning & Oconee National Forest; Semiochemicals from coleopteran host plant hosts, responses Studies were performed to isolate and identify semiochemicals that mediate location of host-infested trees by parasitoids of the southern pine beetle (SPB), Dendroctonus frontalis. Bark or bolts removed from pines infested with SPB broods attracted significant numbers of the hymenopterous parasitoids Spathius pallidus and Roptrocerus xylophagorum to sticky traps placed in an active SPB infestation. Traps baited with the water distillate of SPB brood-infested bark also attracted both species of parasitoids. In contrast, a synthetic bait composed of 18 compounds identified from the headspace volatiles of attractive bark failed to trap parasitoids. The oxygenated and hydrocarbon components of the bark distillate were partitioned by silica gel liquid chromatography, and the resulting two fractions were tested in the field. Parasitoid attraction was greatest when both fractions were released from traps simultaneously. The hydrocarbon fraction, which failed to attract parasitoids, enhanced the weak attractiveness of the oxygenated fraction. Hence, it appears that no single compound is responsible for mediating SPB parasitoid host-tree location and that both oxygenated and hydrocarbon semiochemicals are involved in this process. none