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

Abstract

The viviparous, epizoic African earwigs of the genus Hemimerus are currently regarded as the sister taxon of the remaining Dermaptera (Forficulina). Exoskeleton, musculature, and part of the nervous system of the female abdomen, from segment IV on, are described. The morphological interpretation and homology relations of most components are discussed, using previous and original data on Forficulina, Zygentoma, Ephemeroptera, Orthoptera and Dictyoptera as a comparative framework. In the mid-abdominal segments some interesting similarities with Zygentoma are indicated. Focal issues in the postgenital abdomen are the terminal dorsal sclerites, the cercal muscles, and the paraprocts and associated muscles. Earlier hypotheses on the dermapteran postabdomen (opisthomere and pseudocercus hypotheses) and results from ontogenetic studies are scrutinized. Some interesting features detected in female Hemimerus are the immobilization of terga VIII–X by means of a thick internal cuticle layer, the lack of dorsal muscles on these terga, the shift of some insertions of cercal and rectal muscles from tergum X to tergum IX, and minute pits on the venters IX and X that could be spiracle vestiges. Some of these features occur also in other Dermaptera. Some abdominal characters suggest that Hemimerus is nested within the Forficulina. The lack of the clasper-shape in the cerci is not a strong argument against this.