Phase-Related Developmental Characteristics of Antennal Sensilla of Nymphal Laodelphax striatellus (Hemiptera: Delphacidae), a Serious Virus-Transmitting Insect Vector of Graminaceous Crops

The immature development of the antennal sensilla borne by the first—fifth instar nymphal Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae) were studied using scanning electron microscopy. Sensillar types of nymphs did not vary, but the distribution pattern of sensilla gradually changed during the postembryonic development. Seven types of antennal sensilla were found on the antennae of each of the first—fifth instars. One Böhm bristle and one sensillum campaniformium I on the scape, one Böhm bristle and one sensillum campaniformium II on the pedicel, and one sensillum coeloconicum and three sensilla basiconica on the swollen flagellar base (main body) remain constant during development. The numbers of sensilla chaetica on the scape and pedicel and the numbers of sensilla trichodea, sensilla placodea, and sensilla basiconica on the pedicel gradually increased from the youngest to the oldest instars. In contrast, sensilla trichodea, which occurred on the swollen flagellar base of the first instar nymph, disappeared after the first molt, and one sensillum placodeum on the swollen flagellar base of the first instar nymph gradually degraded during development and finally disappeared after the third molt. The length and width of antennae increased during the development, except for the flagellar main body, which presented negative growth in its width after the first molt. The development of antennae seems according with the need for bearing sensilla.