External morphology and distribution of the antennal sensilla of the stonefly, Paragnetina media (Walker) (Plecoptera : Perlidae)

Abstract

The distribution and external morphology of sensilla on the antennae of nymphal and adult stonefly, Paragnetina media (Plecoptera : Perlidae) were studied with light and scanning electron microscopy. A peculiar arrangement of 3 types of sensilla was observed on the antennae of the nymphs. Thick- and thin-walled sensilla basiconica and coniform sensillar complexes occur in a group, and 6 to 7 such groups are located around the distal margin on the segments in the mid-region of the flagellum. Campaniform sensilla are concentrated in a ring around a crown of thick- and thin-walled sensilla basiconica on the distal end of the pedicel. Two types of trichoid sensilla, long wavy, and stout straight, are present on the flagellum of the nymph. Adult stoneflies have an antennal surface profusely covered only with long and short trichoid sensilla; all other nymphal type sensilla are absent. The lack of nymphal type sensilla on their antennae may be related to the adult's brief, non-feeding terrestrial life.