Structure and morphology of antennal and palpal sensilla of adult long-horned caddisfly species Triplectides indicus (Walker 1852) (Insecta: Trichoptera: Leptoceridae): a scanning electron microscopy study

The mechanoreceptive and chemoreceptive sensilla located on antennae, labial palps and maxillary palps of the long-horned Caddisfly species Triplectides indicus (Walker 1852) (Insecta: Trichoptera: Leptoceridae) were studied by scanning electron microscopy. A total of nine different subtypes of sensilla under six different sensilla types, comprising Böhm’s bristle (BBR), sensilla ampullacea (SA), sensilla chaetica (SCH), sensilla coeloconica (SCO), sensilla trichodea (ST), and sensilla squamiformia (SQ) were observed. Strikingly, no sensilla basiconica were observed on either the antenna or the palps of this species. The absence of sensory zones, and the apparent absence of basiconic sensilla point to a significant reduction in antennal olfactory capabilities in Triplectides indicus, suggesting a lack of structural specialization in sensory structures. This study suggests that, in comparison to other species of Trichoptera, Triplectides indicus’ sensory function is less developed and primitive. This study comprises the pioneer work on exploring different sensilla of Indian caddisflies.