Antennal morphology and sensilla ultrastructure of three Tomicus species (Coleoptera: Curculionidae, Scolytinae).

The antennal morphology and sensilla ultrastructure of Tomicus yunnanensis, T. minor, and T. brevipilosus were studied by scanning electron microscopy and transmission electron microscopy. Eight common sensilla types were recorded: (1) sensilla trichodea (S.tr.) types 1 and 2 were located on the club and were innervated by five and eight dendrites, respectively; (2) sensilla chaetica (S.ch.) types 1 and 2 had no dendrites in the sensilla lymph lumen; (3) sensilla basiconica (S.b.), top-protuberated S.b. and fluted cones (Fl.c.) occurred on the club; and Böhm bristles (B.b.) occurred on the funicle. S.b. were the most abundant and were innervated by 10-14 dendritic branches. Top-protuberated S.b., a new sensilla type, were innervated by one dendrite. Fl.c. were innervated by five dendrites. Only three sensilla furcatea were visible on the antennae of female T. yunnanensis. The possible functions of these sensilla are discussed in relation to their morphology and ultrastructure. No statistical differences between sexes were found in the size and numbers of each sensilla type. Although the three species had similar antennal morphology and sensilla type, sensilla on sub-segments 3 and 4 of the antennal club of T. minor were much sparser than those of T. yunnanensis or T. brevipilosus. Concerning the antennae of T. yunnanensis, there were more S.tr. type 2, S.ch. type 2 and S.b. and the size of S.tr. type 1 and S.b. were significantly greater than those of T. minor.