The hairy crazy ant, Paratrechina pubens (Forel), is undergoing a population explosion on St. Croix, US Virgin Islands. Here, we evaluate the status of P. pubens on St. Croix. In 2002, residents of Calquohoun and surrounding areas in central St. Croix began reporting large infestations of P. pubens. In 2005 and 2006, we surveyed ants at >100 sites across St. Croix. We found 3 geographically discrete populations of P. pubens occupying ∼5% of the island: a main population centered on Calquohoun spread over ∼9 km² and 2 smaller populations occupying <1 km² each. Locals blamed P. pubens for crop damage due to high densities of plant-feeding Hemiptera that tended the ants. Surveys of trees in areas with and without P. pubens present indicated that P. pubens has a significant negative impact on arboreal-foraging ants. The distribution and chronology of P. pubens records on St. Croix suggest that this species is a recently arrived exotic. It is unknown whether P. pubens will become a more serious pest on St. Croix or whether populations will collapse to inconsequential levels.