Ultrastructure on antennae and mouthparts in larvae of soybean hairy caterpillar, Spilarctia casigneta Kollar (Lepidoptera: arctiidae)

Abstract

The present study deals with ultra-morphology of antennae and mouthparts of larvae of Soyabean Hairy Caterpillar i.e., Spilarctia casigneta Kollar with aid of scanning electron microscopy with particular focus on sensilla. This species is a serious pest of beans and causes a serious threat to rice bean as it attacks the lower surface of the leaves of rice bean. The antennae and mouthparts of all instars have been examined to study the distribution and morphology of sensilla. The antennae possess total eight sensilla referable to three types: a) 3 small basiconica on pedicel and 3 large basiconica on flagellum, b) 1 chaeticum on pedicel, c) 1 styloconicum on flagellum. The labrum bears six pairs of sensilla chaetica. Mandibles have 3 teeth and 2 sensilla chaetica each. Maxillae have a single sensillum chaeticum on both cardo and stipe. Each galea has a total of 6 sensilla: a) 3 sensilla trichodea, b) 2 sensilla styloconica, c) 1 central sensillum basiconicum. The distal segment of maxillary palp possesses clusters of 8 sensilla basiconica and 1 sesillum digitiformium. The metrical analysis of significant structures has been documented and the probable functions of these sensilla are concluded.