Two new ants: Pheidole drogon and Pheidole viserion

Credit: OIST

The ant genus Pheidole is huge containing perhaps more than 1000 species. They are widespread across the globe. Most Pheidole colonies contain two castes of workers: the "minor" workers, and the "major" workers, or "soldiers". The latter generally have enormous heads and mandibles in comparison to their body size.

Both new species appear dragon-like due to their large and distinctive spines and were recently found in the tropical rainforests of Papua New Guinea. Although they lacks fire-breathing capabilities, the unique, spiny characteristics of the ants reminded the scientists who discovered them of the mythical dragons from the fantasy series and inspired them to name the ants after the 'Game of Thrones' dragons.

For the experts: The ant genus Pheidole—for all of its hyperdiversity and global ubiquity—is remarkably conservative with regard to morphological disparity. A striking exception to this constrained morphology is the spinescent morphotype, which has evolved multiple times across distantly related lineages of Indoaustralian Pheidole. The Pheidole cervicornis group contains perhaps the most extraordinary spinescent forms of all Pheidole. Here we present a taxonomic revision of the P. cervicornis group, and use microtomographic scanning technology to investigate the internal anatomy of the thoracic spines. Our findings suggest the pronotal spines of Pheidole majors, are possibly skeletomuscular adaptations for supporting their disproportionately large heads. The ‘head support hypothesis’ is an alternative to the mechanical defense hypothesis most often used to explain spinescence in ants. The P. cervicornis group is known only from New Guinea and is represented by the following four species, including two described here as new: P. barumtaun Donisthorpe, P. drogon sp. nov., P. cervicornis Emery, and P. viserion sp. nov. The group is most readily identified by the minor worker caste, which has extremely long pronotal spines and strongly bifurcating propodeal spines. The major and minor workers of all species are illustrated with specimen photographs, with the exception of the major worker of P. cervicornis, which is not known.