ABSTRACT
Pemphredoninae are a very large lineage of crabronid wasps with more than a thousand species. In this lineage, the subtribe Spilomenina stand out for containing the smallest apoid wasps and by exhibiting relatively complex social behavior such as female nest-sharing and even eusocial colonies. One of the most conspicuous features of this subtribe, and which seems to be associated with its social behavior, is the presence of silk spinnerets that are used for lining and nest building. In the present study, we conducted Bayesian inference and parsimony analyses with a subset of a previously established morphological data matrix of Pemphredoninae. Our phylogenetic results indicate that Spilomena subterranea McCoquodale & Naumann, 1988, an Australian spilomenine species that presents nest-sharing behavior but lacking silk apparatus represents an independent lineage, recognized here in a new genus, Australomena gen. nov. Our results indicate that Australomena gen. nov. is sister group of the remaining Spilomenina (Arpactophilus, Microstigmus, Spilomena and Xysma). The females of Australomena gen. nov. shows clear adaptations for ground nesting, such as a pygidial plate and basitibial plates on the hind legs, that means that nest-sharing behavior arose very early in Spilomenina evolution, apparently long before the emergence of the silk apparatus.
KEY WORDS:
Crabronidae; Spilomena; apoid wasps; eusociality; partitioning; homoplasy criterion; social behavior; silk spinnerets
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