Thoracic scent efferent system of the Tessaratomidae sensu lato (Hemiptera: Heteroptera: Pentatomoidea) with implication to the phylogeny of the family

Abstract

We studied the cuticular structures associated with the opening of the adult metathoracic scent glands in the family Tessaratomidae. The terminology previously used for these structures in the Tessaratomidae and Pentatomoidea is briefly reviewed and most suitable terms are selected (i.e., metathoracic scent apparatus, internal and external scent efferent system, internal orifice, vestibule, ostiole, ostiolar groove, peritreme, auricle, spout, groove, ruga, disc, peritremal lobes, evaporatorium, mycoid surface, mushroom body, bridge, alveole, trabeculae, and peritremal surface). We examined and illustrated external scent efferent system of 40 species from 33 genera belonging to all three subfamilies of Tessaratomidae sensu lato, i.e. Tessaratominae, Natalicolinae, and Oncomerinae. Three basic types were recognized: i) Oncomerinae – ostiole slightly removed laterally from the position between coxal acetabula, oval, ostiolar groove not developed or very short, peritreme in form of spout attached anterolaterally to the ostiole; ii) Tessaratomidae sensu stricto (= Tessaratominae + Natalicolinae) – ostiole situated between acetabula, strongly incised mesad, thus vestibule distally opened in two planes (ventrally and laterally) as ostiolar groove, peritreme in form of anterior and posterior peritremal lobes surrounding the ostiolar groove; and iii) Platytatina (Platytatus ambiguus Bergroth, 1892) – ostiole shifted near to lateral metapleural margin, ostiolar groove reduced, situated between two flat, reniform processes (median and lateral lobe). A polarity of these structures is suggested: the type i) of Oncomerinae is regarded as plesiomorphic(shared with Urostylididae, Dinidoridae, etc.); the type iii) of Platytatina is homologized with type ii) of Tessaratominae sensu stricto; the type ii) is unique within Pentatomoidea and considered as an autapomorphy. The information content of the characters of the external scent efferent system and metathoracic spiracle for a phylogenetic hypothesis of relationships within Pentatomoidea is tested by cladistic analyses. We found some apomorphies helping to define Tessaratomidae and Plataspidae, most of the characters, however, seem to be homoplasious at family level. The results of the cladistic analyses further support the monophyly of Dinidoridae + Tessaratomidae sensu lato and that of Tessaratomidae sensu stricto, while the relationships of Oncomerinae and Tessaratomidae sensu stricto as well as the relationships among the family-group taxa within Tessaratomidae sensu stricto need further studies.