Morphology of interommatidial sensilla of Discocephalini (Heteroptera: Pentatomidae: Discocephalinae)

Interommatidial sensilla have been explored for their taxonomic value and other aspects in Diptera and Lepidoptera. In Heteroptera, Eurystethus is the only genus where these structures were examined in delimiting subgenera and species. This study investigates the presence, distribution, and morphology of interommatidial sensilla in Discocephalinae species and discusses the sensilla's value for cladistic and taxonomic appraisals. Twenty species of 18 genera were analyzed: 16 Discocephalini genera, one genus in Ochlerini, and one genus in Edessinae. Species' heads were observed from photographs taken with light microscopy (LM) and scanning electron microscopy (SEM). From these images, we identified eleven types of sensilla, classified into chaetica, trichoidea and coeloconica. In LM, only sensilla chaetica with a length of 40–100 μm were visible, present in six species. Under the SEM at least one type of sensillum was visible in 19 of the 20 species analyzed. No difference between the various kinds of sensilla were apparent between males and females or adults and nymphs of a given species. Both subgenera of Eurysthetus have the same type of sensillum (chaeticum type I), which suggests this is not a delimiting feature. We conclude that sensilla chaetica can be a valuable character to delimit groups of genera within Discocephalini.