SPREAD IN TRINIDAD OF THE SOUTH AMERICAN FIRE ANT SOLENOPSIS INVICTA (HYMENOPTERA, FORMICIDAE)

Solenopsis invicta, a fire ant originally from the grasslands of South America, has become an important exotic pest in the USA, East Asia, and elsewhere. This species arrived by ship in Mobile, Alabama in the 1930s and has since spread across much of the southern USA. Beginning in 1981, S. invicta has been reported from a growing number of West Indian islands, including Puerto Rico (1981), the Virgin Islands (1988), the Bahamas (1993), Antigua (2000), Caicos Islands (2001), Anguilla (2006), St Martin (2006), Barbuda (2007), Montserrat (2007), Nevis (2007), St Kitts (2007), Aruba (2007), and Jamaica (2010). In the present study, we examined the status of S. invicta on the island of Trinidad. Although the first published record of S. invicta in Trinidad dates to 2000, we have reliable records of this species from sugarcane and rice growing areas of west-central Trinidad dating to 1991 and specimens collected in 1993. In 2003-2004, we surveyed ants at sites all over Trinidad to document the distribution of S. invicta and its congener, Solenopsis geminata. We collected S. invicta at 60 sites, all in west-central Trinidad. In contrast, we collected Solenopsis geminata at 158 sites spread across all 7 counties of Trinidad. The highest densities S. invicta populations occurred in County Caroni, with scattered populations extending into disturbed areas of County St. George to the north and east, and County Victoria to the south. As of 2004, S. invicta occupied similar to 10% of the island, but we see no reason why this species will not spread throughout most open, disturbed sites in Trinidad, displacing S. geminata as the dominant fire ant on the island.