The female abdomen of the viviparous earwig Hemimerus vosseleri (Insecta :Dermaptera : Hemimeridae), with a discussion of the postgenital abdomen ofInsecta

The viviparous, epizoic African earwigs of the genus Hemimerus are currentl y regarded as the sister taxon of the remaining Dermaptera (Forficulina). E xoskeleton, musculature, and part, of the nervous system of the female abdo men, from segment IV on, are described. The morphological interpretation an d homology relations of most components are discussed, using previous and o riginal data on Forficulina, Zygentoma, Ephemeroptera, Orthoptera and Dicty optera as a comparative framework. In the mid-abdominal segments some inter esting similarities with Zygentoma are indicated. Focal issues in the postg enital abdomen are the terminal dorsal sclerites, the cereal muscles, and t he paraprocts and associated muscles. Earlier hypotheses on the dermapteran postabdomen (opisthomere and pseudocercus hypotheses) and results from ont ogenetic studies are scrutinized. Some interesting features detected in fem ale Hemimerus are the immobilization of terga VIII-X by means of a thick in ternal cuticle layer, the lack of dorsal muscles on these terga, the shift of some insertions of cereal and rectal muscles from tergum X to tergum IX, and minute pits on the venters IX and X that could be spiracle vestiges. S ome of these features occur also in other Dermaptera. Some abdominal charac ters suggest that Hemimerus is nested within the Forficulina. The lack of t he clasper-shape in the cerci is not a strong argument, against this. (C) 2 001 The Linnean Society of London.