Scanning electron microscopy of antennal sensilla of Aromia bungii (Coleoptera, Cerambycidae) adults and electroantennogram responses to volatile organic compounds.

The red-necked longhorn beetle, Aromia bungii (Faldermann) (Coleoptera, Cerambycidae) is a major pest of Prunus species that has recently been recorded in several countries in Europe. To contribute to the knowledge of the olfactory system of this pest, the external morphology and distribution of antennal sensilla of both sexes were studied by scanning electron microscopy (SEM). Moreover, the chemoreceptivity of the apical (9th-7th), middle (6th-4th), and basal (3th-1nd) groups of flagellomeres to 1 mg of stimulus loads of 11 volatile organic compounds (VOCs), previously reported as bioactive towards other xylophagous beetles, was determined using electroantennography (EAG). In both sexes the antennae are filiform consisting of a basal scape, a pedicel and a long flagellum composed of nine flagellomeres. Based on their morphology five types of sensilla chaetica, three types of Sensilla basiconica, one type of sensilla trichodea and Böhm bristles were identified on the antennae. The strongest antennal stimulants were sulcatol, nonanal, sulcatone, and 2-phenyl-ethanol in males and sulcatone, sulcatol, 3-pentanol, and nonanal in females whereas 1-ethanol and glycerol were the weakest antennal stimulants in both sexes. The mean EAG responses of the antennal apical part were significantly higher (P<0.05; Tukey test) than those of the middle and basal parts for 10 compounds in females and 8 in males. Sensilla basiconica, inferred to have an olfactory function, are present in all flagellomeres but with a patchy distribution and a variable concentration. Moreover, the female 9th flagellomere presents areas where the Sensilla basiconica are organized in very gathered clusters. These are assumed to function as an enlarged odor-sensing area advantaging long-distanc