Diversity of the external thoracic scent efferent system of Carpocorini (Heteroptera: Pentatomidae) with character selection for phylogenetic inference

The metathoracic glands of Heteroptera open through paired orifices ventrally on the metepisternum. Externally, the mesopleura and the metapleura of Pentatomidae are equipped with the external scent efferent system (ESES), structures involved in spreading the metathoracic glands secretions. The ESES of the highly diverse Carpocorini (Pentatomidae) was studied under light and scanning electron microscopy. We present a summary of the morphological variation of the ESES found as a list of character statements, intending to facilitate character coding to assessing phylogenetic relationships among carpocorine genera. The variation on ESES is discussed in the light of the current understanding of Carpocorini systematics. We identified 27 characteristics that were coded for 90 species (63 genera), all characters and character states are illustrated. Three general patterns were recognized: a well-developed evaporatorium on meso- and metapleuron, reaching the lateral margin o mesopleuron; a poorly developed evaporatorium on meso- and metapleuron; and an intermediate condition. Several genus-groups proposed within the tribe, based on general and genital morphology, have consistent ESES patterns. ESES morphology is informative at genus level as congeneric species do not show or show little variation on ESES structures. We suggest ESES should be further investigated and included in phylogenetic analyses in Pentatomoidea.