Revisited morphology applied for Systematics of flat wasps (Hymenoptera, Bethylidae).

The world fauna of the flat wasps (Bethylidae) is represented by about 3,000 valid species. The skeletal morphology of bethylids is still not adequately understood and the terminology is generally not standardized between its internal taxa and with other Hymenoptera families. The same scenario exists in most of the families in this order. To address this problem, we describe the external skeletal morphology of Bethylidae. We review the terms used to describe skeletal features in the Hymenoptera in general and a consensus terminology is proposed for Bethylidae, which is linked to the online Hymenoptera Anatomy Ontology. The morphology of the studied specimens is illustrated with photos and line drawings. We also discuss the morphological variation at both subfamilial and generic ranks. Our analyses challenge hundreds of inappropriate, confused or imprecise terms traditionally used for Hymenoptera morphology. As a result, we have applied hundreds of updates of the terminology available online at the Hymenoptera Anatomy Ontology.

Evolution of Metapostnotum in Flat Wasps (Hymenoptera, Bethylidae): Implications for Homology Assessments in Chrysidoidea.

Some authors in the past based their conclusions about the limits of the metapostnotum of Chrysidoidea based on the position of the mesophragmo-metaphragmal muscle, rather than aspects of the skeleton and musculature associated with the metapectal-propodeal complex. The latter character system suggests another interpretation of the metapostnotum delimitation. Given this scenario, the main goal of this work is to present a new perspective on the metapostnotum in Chrysidoidea, especially Bethylidae, helping to resolve questions related to the evolution of the metapostnotum. This is based on homologies established by associating of insertion points of ph2-ph3 and ph3-T2 muscles with the delimitation of the respective sclerite the muscles insert into. Our results indicate that, according the position of the metaphragmal muscles, the metapostnotum in Bethylidae is medially expanded in the propodeal disc and has different forms of configuration. Internally, the limits of the metapostnotum can be tracked by the shape of the mesopostnotum, and vice versa. Thus, the anteromedian area of the propodeal disc sensu Evans was reinterpreted in the current study as the metapostnotum. In conjunction with associated structures, we provide evidence to clarify the relationships between the families within Chrysidoidea, although certain families like Embolemidae, Dryinidae and Chrysididae exhibit extreme modifications of the condition found in Aculeata, as observed in Bethylidae. We review the terminology used to describe anatomical features on the metapectal-propodeal complex in Bethylidae in general, and provide a list of recommended terms in accordance with the online Hymenoptera Anatomy Ontology. The morphology of the studied subfamilies are illustrated. Studies that focus on a single structure, across a larger number of taxa, are more insightful and present specific questions that can contribute to broader issues, thus providing a better understanding of the morphology and evolution of insects.