Ultrastructure of the sensilla on the larval antennae and mouthparts of Chilo infuscatellus (Snellen, 1890) (Lepidoptera: Crambidae)

The sugarcane shoot borer Chilo infuscatellus (Snellen, 1890) is a major sugarcane pest in Lepidoptera, but little information is available on its larval ultrastructure. Here, the sensilla of the antennae and mouthparts of the mature larva of C. infuscatellus were investigated using scanning electron microscopy. The antenna is three-segmented and possesses two types of sensilla, as well as three sensilla basiconica and two sensilla chaetica on the apical surface of the middle pedicel; three sensilla basiconica on the apex of the distal flagellum. The mandibulate mouthparts consist of a labrum, a pair of mandibles, a pair of maxillae, a labium, and a hypopharynx. The labrum possesses six pairs of sensilla chaetica; the membranous epipharynx bears three pairs of flattened sensilla chaetica, three pairs of epipharyngeal sensilla, and a pair of oval sensilla digitiformia. The mandible is equipped with two sensilla chaetica on the posterolateral surface. The maxillae are well developed, each formed by a cardo, a stipes, a galea and a two-segmented maxillary palp. Each galea carries six sensilla basiconica and two large sensilla styloconica. The maxillary palp is furnished with 9 sensilla basiconica, one sensillum digitiformium and one sensillum placodeum on the distal segment. On the labium, each labial palp has a sensillum chaeticum with apical bifurcation and a thick sensillum styloconicum. This paper briefly discusses the possible function of sensilla on antennae and mouthparts.