Description of the queen caste of Pheidole obscurithorax (Hymenoptera: Formicidae)

Pheidole obscurithorax, the South-American big-headed ant, is native to South America, but now common along the United States Gulf Coast region. Although the major and minor workers castes have been described, reproductive castes have not. The spread of exotic and potentially invasive ant species that disperse by flight can be monitored in part through the use of various aerial and light traps. However, due to a paucity of descriptions of reproductive castes of ants in general, identifications of these castes from traps are difficult at best. To better facilitate the identification of P. obscurithorax and its spread in the Gulf Coast region of the US, the queen caste of the exotic Pheidole obscurithorax is described. Photographs of morphological structures, including wing venation, are provided.