First record of a species from the New World Pheidole flavens-complex (Hymenoptera: Formicidae) introduced to the southwestern Pacific

Ants are among the world’s most destructive invaders, and Pacific Islands are particularly susceptible to invasion by non-native ant species. A species from the taxonomically problematic Pheidole flavens-complex is reported here for the first time from the southwestern Pacific. Specimens of the species reported here were collected November 2011 from an established colony on Espiritu Santo, Vanuatu, during a survey of the island’s ant fauna. Morphological and genetic analyses revealed these Vanuatu specimens belong to the Neotropical P. flavens group. The DNA sequence data most closely matched those of two specimens previously determined as P. moerens Wheeler and P. flavens Roger. A closely related taxon currently being treated as P. moerens Wheeler was reported from Hawaii in 2005. Preliminary morphological analysis suggests that the Vanuatu population reported here represents a different species than the Hawaii P. moerens. However, a valid species name cannot be confidently applied to either the Hawaii population or the Vanuatu population until a comprehensive taxonomic revision of the flavens-complex is completed. Species of the Pheidole flavens-complex are occasionally considered pest ants, but have not been documented as causing significant harm to native species, food security or public health. However, the recent spread of species in this complex across the southeastern United States, recent introductions to California and Hawaii, and the recent discovery in Vanuatu suggests their potential for human-mediated dispersal and establishment. We hope that raising awareness of this new incursion will improve the chances of early detection and eradication before the species spreads further into the Pacific Island region. We provide specimen photographs of the major and minor caste and a brief diagnosis that can be used to separate this species from other Pheidole species introduced in the Pacific island region, including Pheidole megacephala (Fabricius) and the morphologically similar Pheidole parva.