Open Access

Results from a comparative anatomical study of the mesosomal skeleton of Chalcidoidea are presented. External and internal features are described and illustrated for 39 chalcidoid taxa, representing 16 families and 29 subfamilies. This is the most comprehensive morphological study ever conducted for the superfamily. The mesosoma was dissected, macerated and investigated using scanning electron microscopy. The mesothorax and metathorax contributed most of the phylogenetically relevant information. The metafurca is highly variable within Chalcidoidea but seems to be relatively constant at the subfamily level. One hundred and fifty-four morphological characters were scored and analysed cladistically. Outgroup species were chosen from six apocritan superfamilies: Stephanoidea, Ceraphronoidea, Cynipoidea, Platygastroidea, Proctotrupoidea and Mymarommatoidea. Some previously suggested chalcidoid relationships were retrieved: (1) Pteromalidae: Pteromalinae + Miscogasterinae + Panstenoninae; (2) Perilampidae + Eucharitidae; (3) Chalcididae + Leucospidae + Eurytomidae; (4) Eulophidae: Eulophinae + Tetrastichinae + Entedoninae; and (5) Eupelmidae + Encyrtidae, Mymarommatoidea renders Chalcidoidea paraphyletic in our analyses; however, the taxon sample is too restricted to provide a robust hypothesis. Three previously unreported putative autapomorphies of Chalcidoidea were revealed: (1) presence of an exposed, triangular or diamond-shaped prosternum; (2) presence of a percurrent mesopleural sulcus anteriorly terminating in the acropleuron; and (3) presence of paired metapectal plates lateral to the metafurca.

The South American genera of the Cimbicidae are reviewed. Five genera and nine species are recognized. Redescriptions of all genera and an identification key to all species are provided. All species are illustrated, including both sexes and aberrant specimens when relevant. The South American Cimbicidae are grouped in the subfamily Pachylostictinae, but there is substantial morphological divergence at the genus level. This and the isolated geographic and phylogenetic position relative to the other subfamilies of Cimbicidae indicates that the Pachylostictinae have evolved in isolation for a substantial amount of time. Host plant records are known for only one species, Pseudopachylosticta subflavata, which is mainly found in the Chacoan subregion. The distribution of the remaining species falls almost exclusively within the range of the Parana subregion forest provinces, a biome that has been much reduced by human activity in the past half millennium. It is likely that these rarely collected wasps are threatened by habitat degradation.

Abiinae is the second-largest subfamily in Cimbicidae, a small family of true sawflies (Tenthredinoidea). The subfamily is adequately defined, but the generic classification has been unstable. Currently, only two genera are regarded as valid: Abia Leach, 1817 and Allabia Semenov & Gussakovskij, 1937. We evaluate the generic classification of Abiinae in a phylogenetic context. A total of 32 species (out of 57 described for the subfamily), including the type species of Allabia, Allabia infernalis (Semenov, 1896), are scored for 150 adult morphological characters. Results show some resolution, but only few clades can be circumscribed by consistent character combinations. Most of the characters that have previously been used to define genera are not congruent; consequently, most suggested genus definitions appear to be random character state combinations and few natural groups can be identified. For these reasons, we treat Allabia syn. nov. as a junior synonym of Abia and make the following additional taxonomic changes: Abia infernalis Semenov, 1896 comb. rev. and Abia malaisei (Semenov & Gussakovskij, 1937) syn. nov. For the purpose of long-term stability of the classification of Abiinae, we recommend recognizing only one genus, Abia, within the subfamily.