Cuticular microstructures of abdominal tergites and sternites of Cloeon sp. (Ephemeroptera; Baetidae) during post-embryonic development

The postembryonic changes of the external microstructure of the cuticle on the abdominal tergites and stemites of Cloeon sp. (Ephemeroptera:Baetidae) are described. An inventory of the structures as the aquatic nymph grows and becomes transformed into a terrestrial subimago and then an imago, is provided. It is found that sensillar diversity on nymphal tergites increases with development, but remains unchanged on the stemites. While nymphs and subimago possess various types of sensilla trichoidea, sensilla basiconica are apparent on the imaginal abdomen only. Furthermore, the scaled and spiny cuticle of the nymph becomes relatively smooth in the adult stages. The distinct changes which structure and distribution of the scales as well as marginal spines on the abdominal tergites and stemites of the nymphs undergo during development, must find a reflection in behavioural changes of the larvae. Finally, the taxonomic implications of the observed changes are discussed