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 sternites of Cloeon sp. (Ephemeroptera:Baetidae) are described. An inventory of the structures as the aquatic nymph grows a nd becomes transformed into a terrestrial subimago and then an image, is pr ovided. It is found that sensillar diversity on nymphal tergites increases with development, but remains unchanged on the sternites. While nymphs and subimago possess various types of sensilla trichoidea, sensilla basiconica are apparent on the imaginal abdomen only. Furthermore, the scaled and spin y cuticle of the nymph becomes relatively smooth in the adult stages. The d istinct changes which structure and distribution of the scales as well as m arginal spines on the abdominal tergites and sternites of the nymphs underg o during development, must find a reflection in behavioural changes of the larvae. Finally, the taxonomic implications of the observed changes are dis cussed.